In my opinion, the 17 year old should be charged.
Suppose it was not another hunter in the tree, but a Bald Eagle or other protected species?
There still would have been a crime committed.
As for the other idiots cited, not at all sorry for them either.
One of the primary rules of firearms use (as if we need reminding) is to be certain of your target - period!
This kind of thing happens every year - American hunters getting wounded or killed by another hunter. I wonder how this compares with the incidence of bear, moose, cougar attacks on hunters. It is accepted that the most dangerous hunting situation in America is turkey season. As far as risk of death, I bet it is more dangerous here than in Africa!