Thanks for the history lesson! In that context, the right to bear arms makes sense; but it doesn't really make sense in today's context anymore, especially when there has been so many instances of these shooting sprees in the past few decades. As for this guy, I wouldn't be surprised if he'd gone nuts. I mean, no sane person would do something like this. He even booby trapped his apartment.
I have to say though, this movie was going to make lots of money anyway, so I don't think the shooting incident would help in that regard. In fact, it might have generated negative publicity instead.