I said this in a different comment I think but when dean dies he was trying to kill the MC. I think he was trying to do a murder suicide like thing. Remeber he tried to hand feed you with is poisoned hand. The reason the others die except for benson is because the MC was getting closer to them. I don't think he's the main villain in the story there's definitely something else going on. I think the MC will have to stop everyone from killing each other but they don't always know what there doing. The only reason I think this is because of the axe Sal finds in his room.