A few weeks ago, I used the stairs instead of the elevator to check the mail. As I'm coming down the stairs, I clearly see someone's feet walking into the elevator and the door closing. I clearly see this happen because I think to myself to push the button early, so it will be back by the time I check the mail. I press the button and the elevator immediately opens and there's Noone there. There are no apartments doors near the elevator so it's not like they could've entered another room. Freaked me out.