Yeah, I witnessed a brawl when I visited my friend in Vegas last month.
I didn't see the build-up, but I guess the crowd (ie - parents) of Team A were booing a particular kid on Team B. Team B wins. That player jumps over to the crowd and talks shit, then everybody starts brawling.
I don't think it helped that the tournament was hosted by a richie-rich school and involved schools from across the tracks. Maybe it shouldn't matter, but it does.
Mind you, this was MIDDLE SCHOOL basketball.