Criminal Homicide is defined in PA as......
§ 2501. Criminal homicide.
(a) Offense defined.--A person is guilty of criminal homicide if he intentionally, knowingly, recklessly or negligently causes the death of another human being.
(b) Classification.--Criminal homicide shall be classified as murder, voluntary manslaughter, or involuntary manslaughter.
I am not sure criminal homicide fits what he did, but I'm not sure it is ever a good idea to shoot a fleeing suspect in the back. Why not let him go and pick him up later? No, I wasn't there, but if this kid used the officer arresting the driver as a distraction for an escape, I am not sure how dangerous he was. He probably just wanted to get away.