It has a guy with a camra he is doing a documentery on gangs and is at a gang fight video taping it and the people that he is taping are his friends

They tape a bully beating the shiv out of people on Charlie Bartlet. But he isn't doing a documentary. They then sell the tapes to the students including the kids who got beat up.

Maybe Cidade de Deus (2002) , although I think that was about a kid with a camera, not a video camera...