Help with a possibly violent spirit

Hi guys, first time posting on here but I’m in need of help. I have a friend who is not a believer but the experiences he has had in his flat are scaring him. For the sake of ease, I’m gonna call him P. P and I have known each other for nearly 16 years and at one stage, I lived in said flat with him. A bit of info on the flat beforehand, it’s in a small block of 6, his being one of two on the top floor and his neighbour is across a hallway.
As soon as you enter the front door, there are 2 doors to the right, the first is his room and the second is a tiny cloak room. This is where you feel the energy most. You walk in and feel like someone is hiding in there. When I lived there in 2014 aside from one incident (I saw the door open by itself and a voice telling me to get out before the door slammed shut) the energy felt mostly sad. Aside from the occasional cold spot, it was just the watched feeling.
P has reached out and asked me if I can help him. He has had: shelves ripped off walls, books and dvds sent flying, doors opening and closing by themselves, disembodied voices, walls in other rooms being thumped and now it’s grabbing him. He described it as an icy hand that wrapped round his wrist. He has asked wiccan friends to visit (without saying about the cloak room) and had them refuse to enter the flat. He says he feel afraid a lot and finds himself constantly waiting for something to happen.

I have experienced it but nowhere near as negatively as he has and I’m concerned for him. Anyone any suggestions? We discussed trying to get someone to bless the house but he doesn’t believe in any religion and is concerned anything he does will simply anger it.

He has recently set up cameras and motion detectors but it’s only adding to his paranoia.

Anyone any suggestions? Any and all advice welcome