Firearms or not, any time you are the victim or about to be placed in the role of victim, your only goal is to STOP this person from HURTING you. Frankly, you shouldn't even have the time or luxury to stop and think about where and when to shoot. If you have that much time, remove yourself with your feet. If you don't have time, you have no choice but to remove your attacker with your fists, your feet, or your gun.
Our prime purpose in this life is to help others. And if you can't help them, at least don't hurt them.--The Dalai Lama