Head shots: A bullet to the brain will in many cases produce the greatest and most instantaneous incapacitation. But the head constitutes a relatively small moving target. This movement is often made instinctively by bobbing, ducking, or weaving if he sees your muzzle pointing at it.
Upper Torso Center Mass: The sooner you are able to cause major interference with a suspect’s life-support structure by directly puncturing vital organs, shattering bones, or inducing profuse bleeding, the more likely he is to quickly collapse. This will probably require more than one shot and may take many, depending in part on the efficiency of your weapon, your ammunition, and your shot placement.
Some people make the mistake of shooting once and then waiting to see what happens. However, the round may entirely miss hitting that central mass. Statistically, most bullets fired in gunfights do just that. It is also possible that your suspect may be wearing soft body armor.
Aiming at the large, upper torso offers you the best chance of hitting as well as incapacitating the suspect. You want to look directly at the center of his body, at about armpit level, halfway between his breast nipples, where you want the bullets to hit.
However, additional shots may be necessary. Keep shooting until the suspect ceases to be a threat. If he’s armed and determined to shoot, every second he remains on his feet brings you closer to death.
As previously mentioned, if your shots are having no effect, consider the possibility that the suspect is wearing soft body armor.
Keep your head down and keep the faith,