[William Tell]

Robert357 said: "... the shot placement should not be a wounding shot nor a warning shot, but a shot that will immediately stop the attack, which is usually a shot to an area that would normally be fatal."

That's pretty much it. I was taught to fire two rounds to center-of-mass and then, if the attack continues, a round between the eyes.

Physiologically, what stops an attack is damage to the attackers blood circulation or central nervous system.

Two shots to the chest with a suitable caliber will damage the circulation system of the attacker sufficient to lower blood pressure almost immediately and result in unconsciousness. The follow-up round, in the case that the attack continues, is designed to disable the central nervous system of the attacker. A common reason for needing the follow-up is that the person is wearing body armor of some type.

[Secret Agent Man]

Pelvic/groin shots are good too.