16 year old accused with Murder

Summary:
"Loony" Barron was a great man always trying to get kids away from crime, but he paid for it with his life. Loony Barron was in a gang ( crips) and did not want other young kids to make the same mistake he made, Barron would go to school and jails and talked about violence. Loony Barron confronted this 16 year old boy from tagging a wall and the boy ended up shooting and killing Barron. Late that Sunday night the young boy was arrested for muder proved on a cervalience tape from a buisness near by. He was out there helping children from making the same mistakes he made."

Reflection:
Lonny Barron was killed just by asking a kid not to tagg on a wall and ended up getting shoot to death. He was just a great guy trying to help young kids get out of trouble, and from making thr same mistake he made.

Evidence:
Barron helped kids get out of trouble
16 year old kid killed Barron
Kid was tagging on the wall
Police investigated and found a tape showing the incedent

Questions:
Why would the kid decide to kill Barron?

Link:
http://abcnews.go.com/US/wireStory?id=9787241