I had meant to comment on TCB's question, too.
I always thought that shooting to incapacitate, but not kill, was an option that was (or used to be?) practiced whenever possible. Then several years ago I read an article that explained how actually unrealistic that is. And how unsafe, should the danger turn out to be very real. The reasons given were that aiming for a limb is way the hell harder than you might think, and that any advantage given to someone waving a real gun around can be lethal. For these reasons, the writer (who was possibly in law enforcement, but I don't remember) concluded that shooting only to wound someone is a very popular myth among the populace. Cops are trained to shoot to where it will kill, period.