Only his buddies really knew the whole story.
The gang shooting thing was just a cover, because who would really give the real story of ripping someone off in a drug deal?
You just get used to telling it so much that you actually start to believe it.
Almost the same thing happened at my highschool when a kid went bad on a deal, go the shit kicked out of him, then told the cops it was because he stole a GPS.
Not that common of a situation.