The Entity in Cell Block D

My mom and I had been on a tour of Alcatraz with a group of people and we entered cell block D which had been for prisoners sentenced to solitary confinement. My mom being my mom wanted a picture of me in one of the cells, so I entered one of them which was pretty much a small empty cell with a green bed frame in the corner. She wanted me to sit down on the edge of the bed frame for the picture so I did. When I went to stand up after she took the picture, I physically could not stand up. It felt like there was something pushing down on my chest to hold me down on the bed frame and I couldn't breathe. I managed to stand up really quickly and force myself up but I couldn't find my balance. It felt like I was on a boat on the ocean, the floor didn't feel solid. I didn't see anything but I definitely knew something in there wanted to hurt me if I stayed any longer.