I feel for these dumb kids. We shot each other with our pellet guns and BB guns all the time back in the day. You wear a layer or two of heavy denim.
Shouldn't be brought to trial. After all who tries to kill someone with one shot...of a pellet gun...in the back. I mean sure it can happen. If the guy shot him three times in the temple, I'd be less charitable. He'll get suspended sentence if it does, community service and some PTSD.