Sounds to me like your friend Roy needs to enroll in anger management classes, the sooner the better. His problem is not neurological, it's called having a bad attitude and no self control. Bottom line he can't control his temper. That's a choice, not a medical or psychological condition.
When he does that I will begin to have some respect for him. He needs to realize that he has a problem and so do you.
Jay, from my understanding, at one time Roy took a rather nasty beating when he had a store front operation. I believe he has also had a stroke. I never met or knew of him before those incidents. Point is, some of his "issues" may very well have a physical root cause. Not trying to make excuses for him in the least, I think he is an arrogant *****. Just adding some facts is all.