[gnarbarian]

Showing the kid who the bigger man is by forgiving him has a diffusing effect on the situation. It shows compassion and empathy for him, (something the kid initially did not have for the OP). If the kid could produce so much hate out of thin air imagine how angry and hateful he could be if he blamed OP for incarcerating him. (as ass backward that logic is)

[daeken]

Agreed entirely. This sort of thing can turn into a vicious cycle in an instant; by forgiving him, the OP has almost certainly stopped that in its tracks.

However, I can't help but have concerns about the kid's future -- this sort of behavior over a long period screams mental illness -- and sincerely hope that counseling helps.