I've been working in a haunted insane asylum. The place has been under construction for the past 3-4 years. It's a new 1 million square foot building on the insane asylum grounds. I don't think I believe in ghosts, but now that construction has come to an end, weird stuff has been happening that I cannot explain. Locked doors that require a key or RFID badge to unlock, unlocking and opening by themselves, doors with automatic hydraulic door closers holding themselves open, lights turning on and off by themselves, footsteps, disembodied voices, strange sounds, strange shadows/shapes showing up on CCTV feeds, and inanimate objects moving by themselves. All my coworkers have had something happen to them there they can't explain. All the activity started up about 2-3 months ago once construction finished.
That said, I know a few confusing stories too which it wouldn't make much sense for a demon to impersonate the ghost. A friendly ghost who helped a man quit smoking by destroying any pack of cigarettes brought into the haunted house while nobody was looking. Why would a demon do that?
I don't know what to believe, but I also ain't taking any chances by trying to communicate with the dead. Too much risk of accidentally summon a demon.