They should charge the guy that threw the gun to the kid with his Murder.
He gave the gun to the kid that caused the kids death.
The Police Officer did what he had to do when he chased the kid with the gun.
The Officer was protecting him self and everyone else the kid ran past and also any future bad use of that gun from anyone else that was stupid enough to use it in a bad way.
I it to bad that the Officer now has to live the rest of his life knowing that he shot and killed a young teenager.