And this is true no matter what part of their body you aim at.
Absolutely. A few years ago, we had an ND at an oudoor range. The guy put a round of .380 ball through his arm just above the elbow. He knicked an artery and we very nearly lost him. Same goes for the kneecap. There's a big artery right there, and "knee capping" could cause a fragment of bullet or bone to puncture it.
If I shoot someone, there is no way I can guarantee what level of injury I will inflict. Therefore, I must assume that any shot will take a life.
And I have to think and act accordingly.