Couple of things. 1. I'm not talking about punishment. I don't believe in capital punishment, simply because I think it's too emotional of an issue, and because of the risk of innocent people being killed. Yes, I think they deserve to die, and that's why it shouldn't be decided later by other people. 2. I am talking about stopping the situation immediately and permanently. I believe there is a huge difference between shooting someone dead to stop them from harming someone, and restraining them and killing them later at your convenience. One is to ensure immediate cessation of aggression, with minimal risk to whoever has chosen to resist. The other is punishment. Yes, in that situation (and I hope it never happens) I would shoot to kill... at least until they scattered. I find no reason to risk my life (and the life of the victim) in order to preserve theirs (they could be armed themselves after all).