Replying to Roomie just went psycho on me...

So ya, my roomie just went ape shit on me haha. It was so ridiculous. A little background, we knew each other before we roomed together, but not really all that great. Been going pretty well so far, sometimes we annoy each other but not that bad. Anyways, today I'm sitting on the couch reading and he is at his desk. He starts spitting on the floor like every minute or so, he had just had some wisdom teeth surgery.

Me: Dude, that's disgusting.
Him: So? *spits*
Me: Come on man, the bathroom is like 10 feet away.
Him: I don't care. *spits*
Me: Dude come on, seriously. That shit is gross.
Him: I don't care, you clean it up.
Me: Why the hell would I clean it up? Just stop spitting on the floor.
Him: (raised voice) What are you going to do about it? Starts spitting repeatedly. Fucking stop me.
Me: Dude, the bathroom is like 10 fucking feet away, just spit in there.

All of a sudden he just goes nuts. Grabs his chair and chucks it across the room and starts screaming at me. Swearing like mad, saying how his teeth fucking hurt, hes trying to study and hes having a bad week. I'm like "Dude, i'm sorry you're having a bad week, really, I am, but just go to the damn bathroom." He still continues to yell and go crazy like inches from me, fucking screaming. Finally he like yelled himself into silence and I was just staring at him, and he sat down and stopped spitting, haven't talked to him in a while. But WOW, I thought he was going to fucking deck me, and hes like twice as strong as I am, wouldn't have been fun.

Fucking ridiculous though, wtf? How the hell is that a reason to get pissed? I think I must have just set him off from something else.