According to a psychiatrist in sworn testimony, that is what this guy has.
I imagine that he has a foundational belief system that nothing is more important his own rights and his own safety. To the degree that intensely wounding people without regard that their threat to him may have been minimal, it would be in his paradigm, to do (literal) overkill, just as a precaution. And rightly so, from his perspective.
Look in his eyes. He is a man who, oh so likely, very early on, experienced abuses that he eventually learned from; that he must do whatever is in his own best interest in order to survive. And that this supersedes any laws or anyone else’s rights or safety.