>> get out of the way, step back. step back. >> following protocol, inmates on the yard hit the ground and those in the cafeteria take their seats as officers sprint to the scene. >> it was a tense moment when everybody hit the deck. sure enough, they found a weapon and we were right in the middle of it. >> officers catch a gang member attempting to conceal a shank, a homemade slashing weapon. this time, violence was avoided. but nowhere is gang influence more prevalent than out on the rec yards of california's prisons. >> this is a turf war here. everybody's got their own turf and they're not going to let anybody else take it from them. the inmates segregate themselves out here. and the reason being that the gangs want it that way. so a man has no choice but to go with his own type of people. >> it's all run by gangs or at least the gangs think they run the prisons, and then the correctional officers think they run the prison.