Where will this killer strike next?

I'm going to try something new here... this puzzle is going to play out in real-time, so if it remains unsolved long enough the final objective will change. That'll be bad news for some fictional person, but no particular loss for those of you working toward a solution. The story here is long, and a lot of it is just window-dressing, but there's relevant information and a few hints along the way. Get a cup of coffee, take a deep breath, and join our hero as he tries to solve a (hopefully interesting and challenging) new case!

Jump to:   $$\def\T#1{\color{blue}{\small\textrm{#1}}}\rlap{\hspace{400pt}\ref{0651}}\T{6:51 a.m.}$$ (murder $$\rlap{\hspace{400pt}\ref{M1}}\T{#1}$$ $$\rlap{\hspace{400pt}\ref{M2}}\T{#2}$$ $$\rlap{\hspace{400pt}\ref{M3}}\T{#3}$$ $$\rlap{\hspace{400pt}\ref{M4}}\T{..}$$   $$\rlap{\hspace{400pt}\ref{Data}}\T{Data}$$ $$\rlap{\hspace{400pt}\ref{NoCalls}}\T{No Call}\,$$ )   $$\rlap{\hspace{400pt}\ref{1810}}\T{6:10 p.m.}$$ $$\rlap{\hspace{400pt}\ref{2036}}\T{8:36 p.m.}$$ $$\rlap{\hspace{400pt}\ref{2345}}\T{11:45 p.m.}$$
$$\rlap{\hspace{400pt}\ref{628}}\T{June 28}$$

Mr. Peters is a freelance muscle-for-hire sort of fellow, with brains to match the brawn. The past two years have seen his reputation grow significantly following a couple of high profile successes, which he has now parlayed into a pretty decent living as a private investigator with a knack for solving tricky cases. The past few months he's even been called on a few times by the sheriff's office to be a special consultant. (Or, as they like to say in his social circle: he's wanted by law enforcement, and it's a good thing!) Nowadays, instead of waiting for the phone to ring, he can now pick and choose which cases to take. Yes, life is pretty good now.

$$\label{0651}\tag*{\hspace{-400pt}\T{6:51 a.m.}}$$    It's 6:51 a.m. and Peters is mentally charting out his plan for the upcoming day, when there's a knock at the door. Wondering what sort of person would be showing up this early, Peters glances at the security camera monitor, then does a double-take. FBI badges?? Eyebrow raised, Jones ushers two agents into his office. A quick conversation follows, and shortly thereafter Peters is rounding up his things and following the agents into the black SUV waiting outside.

A few minutes later, Peters is sitting with Lead Investigator Martin Cooper in a stuffy office filled with groaning shelves and crammed filing cabinets. Cooper looks like he hasn't slept in a week, and given the number of carry-out containers in the overflowing trashcan by his desk, Peters suspects he hasn't left this office in about as long. Cooper, cursing under his breath, shoves a random looking stack of phone books on the floor to free up some desk space in front of Peters, and clears his throat.

"I asked you to join us here because we think you may be able to help us solve a case that has been a thorn in our side for a long time. Before we start, I should tell you that everything you see and hear here today has to remain strictly confidential. Ok?"

Peters nods, and Cooper continues. $$\label{M1}\tag*{\hspace{-400pt}\T{#1}}$$    "This all started several years ago. In June of 2013, there was a murder. Gruesome affair. No real leads came out of it, except for one—that we, understandably I think, kept out of the press: the killer called my number here at the office, and waited until I was on the line to carry out the crime. I wasn't sure exactly what I was hearing at first but could tell it wasn't good; at the end, I listened helplessly to the victim breathing her last. Then, without having spoken a single word, the killer hung up. From details we were able to verify later, we know the call was genuine and that it was made by the killer at the time and scene of the crime. What I didn't know is why... why make the call at all, and why make it to me?"

Cooper shakes his head and pauses briefly before going on. "We traced the call to find where it came from, and asked the local FBI field office to liaise with the police there. Through them we learned that the crime itself was perfect. No witnesses, no useful evidence left behind, no discernable motive. The local police had nothing to go on; we coordinated with them for a bit, but as there were really no leads to chase, the case went nowhere. After a few months, we wished the local PD good luck and we closed our case-file. $$\label{M2}\tag*{\hspace{-400pt}\T{#2}}$$    "Fast forward another half a year, to March of 2014. One morning my phone rang, and when I answered, it was like a repeat of that first call. Again I found myself listening to killing blows and the death struggle of another victim, a man this time, right up to the poor fellow's literal last gasp. But this time a calm, clear male voice spoke into the phone—a single word. 'Leaf.' And then he hung up."

Peters, who has been taking notes as Cooper talks, underlines "Leaf" with a slightly perplexed look.

"Again we chased down the call source," says Cooper. "To my surprise, this murder was 4 states and over 700 miles from the first! As it was relatively close by to us, this time we headed to the location ourselves and found the local police setting up at the crime scene. Together we found things pretty much the same as the first murder. Lots of physical evidence but all of it the victim's, nothing from the killer. No witnesses, no surveillance, no motive. But the killer's M.O. was clearly the same as the first murder, and of course, there was that phone call. So we knew this was the same killer, but that's all we knew; those calls just left us with more questions than answers.

"Like before, with no leads to follow up on, the local police would add another unsolved murder to their cold case backlog. And we had an unsolved mystery of our own, but active and workable cases soon pushed it to the side, all but forgotten after a few months.

"That changed suddenly in June of that year." $$\label{M3}\tag*{\hspace{-400pt}\T{#3}}$$    Peters glances up from his notebook, sensing a shift in Cooper's tone. Cooper's eyes narrow as he resumes his story. "It was exactly one year after the first murder. Another phone call. Same deal as the first one—I heard the victim struggle in vain, and die at the hands of this... sicko... and then he hung up without having said a word. But when we saw where the call had come from...! That's when we realized this guy is just playing with us. That one word he had said at the end of the previous call? That was him telling us where the next murder would take place!"

Peters looks puzzled. "Wait, 'leaf'? That told you where the next murder would be?"

Cooper grimaces. "Well, it didn't then, but after the fact it certainly seems like he had given us a clue, if only we had known how to use it. Because—well, it's hard to explain without giving away privileged information, so let's just say there was no mistaking how 'leaf' tied in to the third murder. That's a big part of why this murder was a turning point. See, the phone call told us at least three things: that this was the same guy, so now we knew we had a serial killer on our hands; that the reason for him calling at all was that it was part of the 'game' he was playing; and that there were some details that all three murders shared in common, but other details seemed random or left to chance."

Peters taps his pen on his notebook and says, "Well, the devil is often in the details, right?"

Cooper laughs humorlessly. "Right. Here's a detail: this third murder was practically across the country from the second one. Obviously the killer can travel, and is not limiting himself to one city, state, or even region. We knew enough about this guy from the first two crime scenes to have a good idea what they'd find (and not find) at this one, so we didn't go ourselves—we just checked the news reports that day and the next, and confirmed he was still following his same M.O. without deviation and without error. Once again, the local police got nothing they could follow up on, and the three murders were far enough apart that nobody but us even knew these were not just isolated incidents.

"We were in a tough spot. We knew this was a serial killer, but that wasn't something we wanted to go public with until we felt we had a handle on it. We also didn't want to have to admit the FBI was only involved because the killer was calling me every time! So we decided to confine this investigation to a very narrow circle of people we could trust, and started working up as complete a profile of this guy as possible, hoping to figure out how to tell where he'd go next. I mean, there are patterns to what he's doing, but we can't get ahead of it, we can only see how each new piece fits once we see what each new piece is. Because, like with the 'leaf' thing, each murder seems to point to the next one, but in a way that isn't helpful to us!" $$\label{M4}\tag*{\hspace{-400pt}\T{...}}$$    Cooper mutters in frustration, then barks out, "And this guy just keeps doing this! Eight victims that we know of so far. Every one of those additional murders took place exactly on the anniversary of one of the first two, but at some random time roughly during work hours. And every one announced with one of those damned phone calls! The locations all have something in common, but are scattered all over the country with no rhyme or reason to the city or state that we can tell, so it narrows it down about as much as it would if we knew, say, that all the victims were killed at a fast food joint. Each murder appears to forecast the next, but even that is little better than knowing, say, that the next victim would be killed specifically at a McDonald's, but not which one.

"None of the victims had ever associated with any of the others; five of them were killed in the building where they worked, though one was off the clock; one was employed by a cleaning service, and was killed at a client's site; the last two victims were at the crime location on, uh, business, but did not work there. Five men, three women; incomes ranging from \$25k to \$250k a year; ages from 31 to 62; race, color, creed, height, weight, hair color, eye color, blah blah blah, nothing useful in the lot. No, we are pretty certain that the victims themselves are chosen opportunistically, so their details don't really matter. We think the actual devil will be found in these details...." $$\label{Data}\tag*{\hspace{-400pt}\T{Data}}$$    Cooper pulls a sheet from one of the folders before him and places it on the desk in front of Peters.

Peters chuckles. "You must go through a lot of toner."

Cooper sighs apologetically. "Look, my hands are kind of tied here, in that there's a lot of information I'm just not able to share with you. We had to redact just about everything on THIS just to be able to show it to you. The boss thinks this is a waste of time, but there are details—which of course I'm not allowed to divulge—that make the techs back there think there's no way this is random, but that there has to be an underlying pattern to how this serial killer operates. They think if we could figure that out, then the hints this guy's been dropping all along the way would help us get ahead of him for once."

Peters studies the paper for a minute. "Well, I do see that there's been at least one murder every year. And that murders in March come with a message, and those in June do not?"

Cooper smiles briefly and nods. "Yeah. I should explain that the March call two years ago was made from a burner phone with a cloned cellphone number. Specifically, my cellphone number. I honestly have no idea why this guy decided to make me his personal G-man, and have a feeling I never will. Anyway, I was dreading answering that call, coming as it did on that particular date and with my own number on it when my cellphone was in my pocket; it was a sure bet to be him. Imagine my relief at answering and not hearing the tell-tale sounds of a life ending! No, this time it was just that same calm, clear voice saying the word 'Union' and hanging up. A few days later, the burner phone in question showed up here in the mail, with a print-out taped to the display that read "UNINO". After the bomb squad cleared it, our techs did their magic and found..." Cooper flips through a few pages in one of his file folders. "Ah yes. The phone was used only once, to make the call to my desk; the call was made from Perry, Florida, at or near the intersection of Hampton Springs Avenue and Byron Butler Parkway. Er, I probably shouldn't have shared that information, so... let's pretend I didn't."

Peters quickly jots down the details with a grin, and asks, "So what about these two 'No call received's?" $$\label{NoCalls}\tag*{\hspace{-400pt}\T{No Calls}}$$    Cooper seems to wrestle with himself for a moment, then clearly makes up his mind. "That first one, June of 2015, I spent the whole day irritably waiting for the damn phone to ring. It never did. I tried to monitor news that day. And the next day. And the day after that. Not a peep. I'd just started hoping that our guy had gotten himself arrested somewhere, or had decided to quit his game, or someone had decided that for him. But no such luck: later that week I got a cheap prepaid phone in the mail, with an enclosed note designed to get my attention, and let's just say it worked. The bomb squad wanted to blow that phone up but I managed to talk them out of it, and after they finally decided it posed no risk, we gave it to the techs. When their report came back, we learned that it'd been turned on for three days, during which it had moved somewhat erratically around Schuylkill County, Pennsylvania. The first day it had been used once, to call (717) 647-2566. The second day it was not used at all. And the third day it was again used once, to call (570) 277-6800. There was one number in the phone's contact list—mine (under 'MEAN ONE'). No prints, nothing else of interest."

Cooper repeats the numbers again so Peters can get them down in his notebook. Then he adds, "As for the second one, in March of 2016, we got nothing. Literally. No contact made whatsoever. After a week of monitoring the news and a month of nothing by phone or mail, I thought maybe he really had stopped this time. But that June, my phone rang right on schedule, and we were back on the case."

Peters glances over his notes again before looking back up at Cooper. "Ok, I think I got all that down. Obviously you're hoping I can make some sense of all this, and find the method to this creep's madness." Cooper nods. "And you're not allowed to tell me the locations or dates of the murders." Another resigned nod. "But I take it from the level of activity and tension around here, that the date is soon. How long do I have to figure this out?"

Cooper glances at his watch. "Um. Not long at all. If we lose another one without results there's going to be hell to pay. We've been working exclusively on this for the last two weeks, and I haven't been home since Monday. But we've gotten nowhere, and finally the boss agreed to let us bring you in to consult. We're desperate."

Peters grins. "That's very bad for you. And very good for me. This is going to cost you big time!"

With a chuckle, Cooper says, "You figure this out and I'll make sure they pay your bill, if I have to take up a collection from the team myself. We all just want to put this madness behind us!"

Peters cracks his knuckles. "Is there somewhere I can work, with a computer and Internet?" Cooper calls one of the techs to get Peters online, and a few minutes later the only sound from Peters' borrowed desk is the faint beats of music from his earbuds and clacking of keys as he madly Googles anything he thinks might help him in his quest....

$$\label{1810}\tag*{\hspace{-400pt}\T{6:10 p.m.}}$$    It's about ten past 6 p.m. and Peters feels like he's gotten nowhere, and fast. He made some good progress in the morning but then stalled, resorting to trying one wild guess after another in the desperate hope of stumbling into a solution by serendipity. Now he is visibly frustrated as he looks back over the sheets of notes he's made thus far. He knows there must be some detail he's missing, but right now he's feeling like he's just going around in circles. He decides to stretch his legs, and sets off to get another soda.

A phone rings. Peters stops, mid-stride, and looks into Cooper's office from whence the telephone's shrill jangling demands attention. Cooper's face has gone ashen. Peters swallows hard, and changes course.

Cooper stabs at the speakerphone button.

"This is Deputy Commissioner, Linda Stuart from Social Security Administration, this is in reference to suspend your existing social security number ...." says a robotic voice from the phone. Cooper yanks the handset up and slams it down, cutting off the call. The entire office takes in a collective breath of relief, before Cooper spouts off a stream of colorful metaphors any sailor would be proud of.

But despite this reprieve, Peters now knows for sure that time is running out for him, for Cooper, and for some as yet unknown victim somewhere. He sits back down, knowing that the phone could ring again at any time ....

$$\label{2036}\tag*{\hspace{-400pt}\T{8:36 p.m.}}$$    Peters sits upright like a bolt, realization suddenly striking him. It's 8:36 p.m. and he's been working on this all day but he feels a surge of adrenaline give him new energy. "I ... I think I've figured it out!"

His fingers fly over the keyboard now as he clicks furiously between tabs, checking and confirming. "Yup ... and yup .... and that means ... oh, no wonder .... and that one, well, that's weird but I get it .... ok but, what about right now? ..." After a final search or two, Peters shouts "I know where he's going!" as he scribbles out a name and address and tears it from his notebook....

... just as the phone rings.

As the team of techs in the back activate the tracing and recording devices, Cooper resignedly presses the speakerphone button. Into the silence that greets him from the other end, he announces his name. Peters, halfway to the office with scrap of notebook paper in hand, feels the blood run out of his face at the sounds that then emanate from the speakerphone. At some point in the next few minutes the paper falls from his hand, forgotten, as he slumps against the nearest desk. Nobody should have to hear anything like this. Cooper has heard it now nine times.

When the last horrific sound has faded away, Peters hears a calm, clear voice utter one word, "Salem." Then the call ends.

$$\label{2345}\tag*{\hspace{-400pt}\T{11:45 p.m.}}$$    It's a quarter to midnight. Peters, drained physically and emotionally, is finally collecting his things and heading for home. He's explained what he found, and showed Cooper and his team the location he had written down on that scrap of notebook paper just before the call came in. Cooper's team quickly verified the location he'd found matched what they traced the call to; just a short time ago, TV news reports confirmed the murder and enough details to dispel any doubt that this was their killer's handiwork.

At least now, when the murderer shows up to claim his next victim, Cooper's team know exactly where to be waiting to finally give their devil his due.

$$\label{628}\tag*{\hspace{-400pt}\T{June 28}}$$    Friday evening. Peters sits down in front of the TV with a drink to relax after a dull day shadowing some analyst for the trading firm he works at and is probably embezzling from. He clicks on the news to see coverage of an arrest of an alleged serial killer at a Los Angeles church. Peters smiles, puts his feet up on the coffee table, and makes a mental note to call Cooper on Monday.

Where, exactly, did the final murder take place?
Where, exactly, will Cooper's team be — and on what day — to catch their man?

• SO LOOOONG O_O SO AMAAAZING Mar 14, 2019 at 23:12
• Count on me to ask really ridiculous questions, but could I ask Mr. Cooper how he defines "creed"? Does he mean "relgion" or "variations within a certain religion"? @NudgeNudge and his speedy detective work is of course why I ask. Mar 14, 2019 at 23:41
• @Brandon_J Don't read too much into it. The use of "race, color, creed" is fairly idiomatic for the idea of all-inclusivity, and that's all Cooper means by it.
– Rubio
Mar 15, 2019 at 2:43

Solution

The phone numbers all belong to churches in different towns across the United States. The pattern here is that ZIP codes of those towns follow the digits of Pi when the murder was committed in March, while June zip codes follow the digits of Tau (2*Pi).

It's reasonable to conclude then that the dates when the murders occur are March 14 (Pi day) and June 28 (which would be Tau day).

Following the murderer's path, we can confirm that the last murder (2019/3/14) took place in Crumb, Tennessee, while the final one (2019/6/28) took place at Salem Baptist Church in Los Angeles, California.

Unfortunately, while the mystery is solved, there is still a loose end. It was easy to deduce the exact location where the next June would take place since the killer was kind enough to leave a message that greatly reduced the possibilities. However, the same can't be said about the March murders, and I reckon there has to be a way to pin them down too.

Locations:

Googling the phone numbers, they seem to all belong to churches

1st Murder: 2013/6/28

- St. Charles Catholic Church in DuBois, Illinois
- Phone number: (618) 787-2781
- Zip code: 62831

2nd Murder: 2014/3/14

- Resurrection of Our Lord Catholic Church in Savannah, Georgia
- Phone number: (912) 232-5258
- Zip code: 31415
- Message: "Leaf"

3rd Murder: 2014/6/28

- Turning Leaf Church of the Nazarene in Glendale, Arizona
- Phone number: (602) 743-3790
- Zip code: 85307

4th Murder: 2015/3/14

- Crossline Community Church in Laguna Hills, California
- Phone number: (949) 916-0250
- Zip code: 92653
- Message: "See You Next Tuesday" (This means the killer knew that the pattern he was following meant that he couldn't kill again until 2016/6/28, which is in fact a Tuesday)

2015/6/27 (NO DEATH)

- Grace Evangelical Congregation Church in Muir, Pennsylvania
- Phone number: (717) 647-2566
- Zip code: 17957

2015/6/28 (NO DEATH)

A murder should have taken place this day, but the zip code that would fit the pattern, 17958, isn't an existing US zip code, which is why he called from churches with the adjacent zip codes on the 27th and 29th.

2015/6/29 (NO DEATH)

- Holy Cross Church in New Philadelphia, Pennsylvania
- Phone number: (570) 277-6800
- Zip code: 17959

2016/3/14 (NO DEATH)

He skipped the March 2016 murder because the corresponding 58979 zip code doesn't exist (or in fact the whole 589xx block of zip codes, which is why he didn't call at all unlike the last time).

5th Murder: 2016/6/28

- Mindenmines Christian Church in Mindenmines, Missouri
- Phone number: (417) 842-3191
- Zip code: 64769

2017/3/14 (NO DEATH)

- A church near the intersection of Hampton Springs Avenue and Byron Butler Parkway in Perry, Florida.
- Phone number: Cooper's
- Zip code: 32348 (Note that the next digits of Pi would have been 32384, another invalid zip code. The UNINO message, with the two last letters flipped, is probably explained by this).
- Message: "Union/UNINO"

6th Murder: 2017/6/28

- Walton Union United Methodist Church in Walton, West Virginia
- Phone number: (304) 577-6997
- Zip code: 25286

7th Murder: 2018/3/14

- Hartsburg United Methodist Church in Hartsburg, Illinois
- Phone number: (217) 642-5425
- Zip code: 62643

8th Murder: 2018/6/28

- Crossroads Baptist Church in Lorena, Texas
- Phone number: (254) 857-3512
- Zip code: 76655

9th Murder: 2019/3/14

- Either Crump Baptist Church, United Pentecostal Church or Crump United Methodist Church in Crump, Tennessee
- Phone number: ???
- Zip code: 38327
- Message: "Salem"

2019/6/28 (NO DEATH, KILLER CAPTURED)

- Salem Baptist Church in Los Angeles, California
- Zip code: 90057

• I have two thoughts regarding the churches... the murderer doesn't seem to be targeting the denominations in any predictable way as of now... either he's attacking another Baptist church, or perhaps a Presbytarian church (since that's the other major denomination he hasn't targetted quite yet) Mar 15, 2019 at 0:30
• Also I believe the murders happen on Tuesdays... but why? Mar 15, 2019 at 0:43
• @North The murders are not confined to Tuesdays. (Shown trivially in that the last one happened yesterday, a Thursday.)
– Rubio
Mar 15, 2019 at 14:11
• @NudgeNudge this is nearly all there. Germany is not involved; that was a complete coincidence. March ‘16 skipped because the entire 579xx block is unassigned; for the others, where the specific number doesnt exist, a call was placed from the general area it would be in, but not a murder. A final thought: you might get slightly different names for the same place, depending how you search, partly because over 6 years some names have changed. A map might help.
– Rubio
Mar 15, 2019 at 14:18

Part 1: The dates

This something really interesting I found out, and it's regarding the dates.

Freakishly enough, the calender dates for June of 2013 is identical to that of March 2014. So if June 13, 2013 is on a Thursday, then March 13, 2014 is also on a Thursday. The killer seemed to have skipped 2015-2016 because 2016 was a leap year.

Another point related to calenders

The lunar cycle also oddly relates to the dates, except in alternating cycles. Here's what I mean. On June 8th, 2013, it was a new moon. On March 8th, 2014 however, it was the end of the first quarter, meaning it was one moon phase ahead. However, the moon phases in June of 2015 and March of 2016 don't align. The same goes for June of 2016 and March of 2017, where none of the dates align. However, they fall into the alternating cycle again in June 2017, where the first of that month was the 1st quarter of the moon phase. And (you guessed it!) March 1st, 2018 it was a full moon (or second quarter of the moon phase).

In conclusion

The murder has to happen this month. It has to be after the 14th, though. I think the dates/how the times of the murder is important to the location. The murderer gives the clues in March, because the cycle restarts in June. So if we could connect the dates to the location... that might give us our lead we need.

Other thoughts, though this part might be irrelevant

Maybe the murderer is like some weird werewolf that attacks only during like June and March. I'm not sure about anything more significant, besides the fact that Daylight Savings start in March and Summer Solstice happens in June.

EDIT:

I just realized Spring Equinox happens on March. March 20th, to be exact. Summer Soltice happens on June 21st. Another significant fact: This year, Spring Equinox happens on the same day as the full moon... relevance?

• The latest update indicates your conclusion is in error.
– Rubio
Mar 15, 2019 at 3:47