If he's obsessed with hunting, he has probably watched hunting on television. He is at least okay with the idea of killing a deer and watching it die. However, as we all know so well, it's MUCH different in person.

My personal biggest concern with a youngster would be their attention span and ability to sit quietly for long periods of time.

As far as watching a deer die, it all depends on the individual. I think he will be fine on the basis that he already has a strong interest in hunting.