 I think your categorization is fine. I have no real dispute there. And I think you're right that we probably, at a moment like this, should draw distinctions between a nutjob who thinks he's doing it because he wants to impress Jodie Foster, as in the Hinckley attempt, or the guy who was trying to shoot Gabby Giffords who believed that grammar was a form of mind control. For lack of a better term, we can classify them as cuckoo for Cocoa Puffs, people who like nothing in their world would ever make sense to us.