Something CREEPY just happened to me. I had to free Johnny Vincent for the mission, and I took the time to study everything in Block C. As I was just before the Biology skeleton, I heard a voice in a loudspeaker ! Really scared me, so much I can't remember what it was saying...
Note that during that mission you can fight with convicts without getting trouble, and the way they fight is... Disturbing. They are like animals, ready to jump to bite you. I recommend you to go and see it.