[discostu]

2 in the 10 is standard firearms defense training, for cops and citizens. Shooting low means you're aiming at highly mobile body parts without a lot of mass (to stop the bullet) and if you miss you're hitting the ground (often concrete) at an angle condusive to ricoche which will send to bullets to areas you can't see. That's bad. You aim for the center mass, it doesn't move as quick, is good at stopping bullets, and if you miss there's nothing to redirect the bullet so you can see what else is at risk while you're aiming.

[Grando Calrissian]

Yes, and (independent of adrenaline) one shot center mass should always be enough. Of course there really isn't a lot of difference getting shot once center mass and getting shot 10 times center mass. You usually end up dead in both instances.

This is why we need to remove the endocrine gland from all cops.