While I agree with the spirit of what you said, I don't think that anyone has any specific ill will towards the young man who shot the pig. Yes, we all have made bad shots in our life, and so too has this young man.
However, I can't help but analogize this situation with a dangerous game hunt in Africa. In this case, the young man is like a hunter in Africa, and the boy's father is like a PH. If a hunter in Africa takes a shot at a cape buffalo, then the PH is there as a back-up to shoot it to make sure that it goes down and doesn't harm anyone. But even if the game was a kudu, or any other animal, a PH is there as a back-up to make sure that the animal does not run off at a bad shot and subsequently suffers.
Here too, the father had 16 opportunities to put that dangerous animal down. And for anyone to say that a 1,000 pig is not dangerous - feral or not, is rubbish. Heck, I have been charged by a 150 pound feral pig and he was a nasty, mean son-of-a-gun. I can't imagine what could have happend if this 1,000 pound monster started to charge anyone!
And even if it wasn't such a monster, the father had 16 opportunities to at least make sure that the animal did not die such a long and painful death.
16 shots at an animal with a .500S&W? We are not talking about ONE bad shot. We are not talking about 2 bad shots. We are talking about 15 bad shots. That means that the boy went through at least 3 sessions to reload the 5-shot revolver. The father/PH should have stepped in. Just my honest opinion.
Zachary