[David Park]

Personally, I see nothing wrong with the double-tap against an attacker with a gun (especially since I carry "only" a 9mm). Shoot-assess is fine, but if assess consists of "can he still pull the trigger?" then I'd like to make as sure as possible that the answer will be "no". Also, I think police are often taught the double-tap, and it was taught in my CCW class, so that can be used as proof that it's not a "bad" technique. If I was carrying a .22, I would probably empty the gun and assess while reloading.

I would not run from a gun-wielding attacker unless I saw him coming from a distance, mainly because I don't want to turn my back on someone with a ranged weapon. My first option would be to seek cover, but otherwise if I could get off the first shot I'd probably shoot it out.

The head shot is always a stopper (assuming a powerful cartridge) but is a relatively small target. A center chest shot has more margin for error. Against an attacker with a knife or contact weapon, a pelvis shot will immediately drop an attacker. They're not totally incapacitated, but they'll have to crawl after you. As CWL said, never talk of killing, talk of stopping the attack. This becomes more important if using a knife for defense, because you have more control over your "aim." Stabbing the heart works, but destroying the weapon arm is preferable, at least in front of a jury.

Don't rely too much on military manuals, or even Col. Cooper (he has the military mindset in some cases). Combat and civilian life require different tactics. That's not to say studying combat skills is bad, just know the difference between silently slitting the throat of a sentry and fighting off a mugger.