Dispute over loud music? = Stupid.
Leave the scene? = Really stupid.
Then, to be tracked down by the police? They charged him with second degree murder. Duh!
I suspect he was really drunk, which was probably one of the reasons he left the scene. Actually, it was probably one of the reasons the whole thing happened.
When I took a class on CCW and the law, one thing that was stressed is that in the eyes of law enforcement, flight=guilt. After a self-defense shooting, you MUST be the first to call 911 and report the incident.
This does not mean you are required to stay in a potentially-dangerous location. If you think the thug's friends will shortly show up, it is OK to leave the immediate area in order to get to a safer location (like the police station) in order to get in contact with the police.