No, we can't guard against the random lunatic. And the fact that dude apparently had an AR-15 doesn't change my opinion that everyone who registers should be issued an M-16 and trained in its use. That's what the Second Amendment is about: To keep the government in it's place and to keep King George III out of your wife's undergarments.

That said: It doesn't change my position that we can and should ban all these cheap ass saturday night specials that are behind most of the violent deaths in America. Again: It's pretty fucking hard to knock over a liquor store with a Kalashnikov.