It does beg the question why he was attacked like that and it looked personal, although them stealing his shoes looked more like thievery. It may be gang related, who knows.. although I know that in ideal world violence like that wouldn't be necessary either way. The biggest reason why gangs exist is because of snowball-vendetta effect - one kills the other, his friends take revenge, and everybody starts taking revenge in turn until the groups form a gang and declare "war" which basically means mindless killing... the story of almost every gang's birth.