I work in an office in a hospital which used to be the oncology ward. Occasionally something weird happens but can usually be explained away by something tangible. Last Sunday morning I was early to work and I was the only person in the building which requires a swipe card to gain entry. While the computer was booting up I walked around the corridor to the kitchen to make coffee and as I passed the male toilet the door suddenly slammed shut very, very hard, as if it had been kicked. The doors in this department are all very heavy and hard to push open or closed. I gathered my courage and opened the door, there was no one there.
The department is completely enclosed with no way to open windows so there was no breeze (not that a breeze would have been enough to close the door anyway). The air conditioning is quite often turned off on the weekends as well but to be honest, I didn't think of checking whether it was on. I admit to being very spooked and was grateful when my big strong male colleague arrived. I KNOW that something weird happened and now I'm wary of entering the department. I have never heard of a ghost hurting anyone or killing anyone but I'm scared anyway.