Escape Room 076: Camera 4

Something is off in the building where we are located, so we decided to install some security cameras. On the footage of Camera 4, we happen to see a strange fellow every once in a while. He seems to be familiar with our building and to know where he is heading. Every time, he goes through a door where even we have never been before… We have already peeked inside. It seems like someone lives there! We are quite worried about this situation, so we are looking for some people who would like to explore what is happening behind this door… We will be very grateful for your help!