The kid was only 15. If this happened to a 30 year old that was a legitimate threat, I would not be sympathetic. But a 15 year old is still young enough to grow up and be a good citizen. I don’t completely understand what happened, but it seems to me the dog should not be attacking someone that is on the ground with a cop on top of him. Also, how much of a threat is a scrawny 15 year old punk? It smells like excessive force to me.
If he's out stealing cars and running from the cops, and his mamma doesn't see fit to criticize that behavior but just blames the police for their actions while arresting her little felon, he may well already be on his way to a permanent life of crime.