but they are taught to make sure their shots are the most effective in eliminating the threat. If you only have one shot to take down your attacker, you want to make sure you hit the biggest target area with the best chance to take them down. Shooting at limbs, etc. is not a very good target because (1) the chances of hitting and immobilizing them is lower, and (2) immobilizing one limb doesn't necessarily eliminate the threat of the officer or others being harmed.

That said, if the aggressor has a gun, multiple shots may be necessary to eliminate the threat. If the aggressor has a less lethal weapon, one or two shots should do the trick.