Alright, time for some knowledge to be brought in.
When defending one's self with a handgun, or any weapon, you keep firing, or swinging, or what have you till the stop. Not till they die, not till you hit them, till they STOP.
If the man, who had been punched in the head, even could land a leg-shot, that isn't what you do. You shoot center mass till they turn and run, or fall down.
Besides, HP or no, adrenaline and other drugs can negate the fact that the attacker got hit.
Also, those saying "But why did he have HP rounds?", it's so that the round doesn't exit the body, potentially hurting someone else. And yes, they cause more damage, but THAT'S WHAT A BULLET DOES.
And about whether the kid deserved it? Yes. He deserved whatever retaliation the victim could bring, and in this case, it was almost half an inch of stopping power. His death is on his own foolish hands.
I would have done exactly this, with one exception; I'd have shot at them both, unless I saw the kid running. You fire on whomever is the best target that is actively endangering you. Not choose by age, gender, race, and if it would be "politically correct".
And finally, how is this any fuel against the 2nd Amendment rights of US citizens? I'm thoroughly confused by that asertation.