I had a experience once, My mum is a manager at a old peoples care home, one night last year she was doing a nightshift, i was out with my mates somewhere driving, she rang me and asked to bring her kebab up to her, so i done so, was sat down at the nurse station on the top floor, the building is like a L shape and the nurse station at the bend so you can see down both corridors, there ae fire doors etc and all were open. I pressed the buzzer to get in mum let me in as she was on her break i was sat at the nurses station talking to her and her mate. One of the buzzers went off down the corridor and mum went to look and the woman was asleep and there buzzer wasnt even plugged in! so mum thought nothing of it came back and told me, sat down eating her kebab and it went off again, mum went to see again same thing happened again. This time she was abit worried as to what it was. so came back and sat down and we were all looking down the corridor and a woman that looked like the nurse walked out the room and walked down the opposite way to the flight of stairs at the end, so mum went to talk to the nurse to tell her what happened, got to the stairs and no body was there! and this was all in a Well lite corridor. just to confirm this mum went down and asked the nurse as to what she'd been doing, and she replied "i have been hear for 35mins getting the tablets ready for the morning" and not moved the whole time. Now me mum and her mate seen this and cant explain it.
I got up and left straight away!