Kids do really stupid stuff.
I finally learned my lesson once when I was 14 (18 now), when I carved my name in a tree at a state park with my cousins, and a park ranger walked up and eventually, we had to go to court! Dumbest thing ever, but I at least think about what I'm doing before I do stuff.
I would be pissed, and I would charge him as much as I could, but he probably has learned his lesson as everyone said.
Good thing you had witnesses behind you to see.