We were a very happy family of $3$ members, me and my mother and father. Sometimes my parents would go outside to visit my grandmother and I used to live alone freely, doing my work and reading storybooks in my freetime. However one day turned out to be creepy.
One day, my parents went out to visit my grandmother and I was alone in my room, doing my schoolwork . My room was in upstairs, and suddenly I heard some faint footsteps on the ground-floor. I could not understand what it was, as the entrance door was closed, so I went down to inspect the floor. To my surprise, there was some muddy footsteps in the floor and it vanishes to a back-door (which was closed) behind my house !
I immediately called my parents to come soon, and when they came after $5$ minutes, after opening the entrance door, my parents and I together now heard the same footsteps from a room, and the entrance door got closed by itself. My parents, terrified, immediately called the police instead of checking the room :-
My Father :- "Help Please, we are stuck in our ground-floor and there is someone in our house, we cannot get out from our back-door as the attacker\burglar is very near to that room !"
Police :- Don't worry sir, keep patience, $2$ of our cops are immediately coming to your house.
Without no hesitation, after $2$ minutes a patrol car with $2$ police officers came outside the house, broke open the entrance door, followed the muddy footsteps (which they saw on the floor) , and went in the room from where the footstep ended.
After some minute or so, they came out saying to my father :-
There is no one in the room, if there would have been someone, then they would have left by the back-door, but it was closed. I think it was some kind of illusion you or your son has seen, but not to worry as we will check every room.
They checked every room of our house, and replied that there was no one in the house, and left. Also, I checked to my back-door, and it was closed.
My parents did think that maybe it was just some other sound (or some illusion), but I did not think that for a second.
What happened in real in my house?
Hint $1$ :-
If you missed something, read the story again. Yes, you heard me right, read the story again.
Hint $2$ :-
I reduce this to $5$ options. Which option shows the most suspicious part? (i) The parents entered the house unexpectedly. (ii) How did the muddy footsteps come? They show the shape of the feet of a man and it must be that someone had entered, but where did he go? (iii) The police had a plan on the family, why would they come as soon as they made a call? (iv) The back-door was closed, there was no one inside the house. It should be some illusion or some other noise. (v) The person who came into the house did not come to murder/steal anyone/anything. He came as a tracker to the house.
Unfortunately no one found the answer here and instead closed my question out of nothing, but still I am going to reveal it here.
Answer:- If the family called the police on an emergency, how did the police know their address? It was also odd for the police to know that this was an illusion or so, and why did the police didn't think before that the back-door could have been opened, and instead it was closed? The tracker who came in the house was someone from the police, and the police had already planned something on the family's house.