Confronting impossible people (In life and business)
sharpn: Try to talk to him about it another time, when you are both relaxed. He's likely got himself worked up into anger over the 'other housemates' (which to him could include you) before doing something that childish.
It will be much harder for him to behave like that once you have discussed it calmly - although if he is 100% a-hole that might not matter much. Also, try to discover the root cause of his annoyance - he might have a justified complaint that just hasn't affected you yet. Good luck!