and forced stateville to undergo drastic reform. >>> coming up, a mass murderer's exploit at stateville sparked massive prison reform. that's next on "lockup." >>> you know, i regret what happened back during the past. but, i mean, everything happen for a reason. you know, it brought me here at a young age. it taught me a lot, opened my eyes a little bit more. so get out there and try to do what's right for my little son and everything. >> by the early 1990s stateville was one of the wildest and most violent prisons in the country. it was a tough place to be for both correctional officers and inmates. all of chicago's most powerful gangs flourished here, continuing the same business they'd been busted for on the outside. the strong preyed on the weak. >> you fought for territorial rights and for what was yours and didn't let nobody take nothing away from you. >> it was almost like a question mark of whether you really wanted to come sometimes. you know, it was a little wilder, a little less restrictive, the movement and everything. >> then in 1995, the entire world got a firsthand look

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every day he puts it right back on. >> this is unit "i," the segregation unit at stateville correctionalnter. basically, this is where the bad people, being extra bad in the facility, come to be locked up. they urinate, bowel movement everywhere, i think they just kind of have gone crazy, prison life is probably getting to them. >> but we've never seen a more bizarre display of the gut churning activity than at california state prison corcoran. it happened during a routine shoot at the prison hospital. >> we were there for like ten minutes. did a couple interviews with a couple of doctors. initially it seemed like it was going to be mundane and going through the process. so we decided to leave. we were all packed up ready to go back into the other section of the prison when all hell broke loose. >> we have four inmates in four different cells that are holding food trays, some of them have started flooding the tier which means they're causing the toilets to back up, causing water to come onto the floor. i'll first go out, try to talk to the inmates and trying to get them to comply with st

despite all of their reforms, stateville is still a very dangerous place. for msnbc, i'm john seigenthaler. >>> there are 2 million people behind bars in america. for the next hour, we open the gates. "lockup." >>> the number of units here at san quentin has grown beyond the capacity of this prison and what it was designed for. >> free us. free us. >> i took sociology in college. and you can stack a bunch of rats together. eventually they start eating each other. >> with the age of the building the way it's set up, almost anything you do, you're in direct contact with the inmates. >> it doesn't matter how much staff we have. they will erupt if it's going to. >> mentality of most inmates, have issues, i'm on death row, and there's nothing you can do to me. if i assault you today, there's nothing they'll do to me tomorrow. that's their mentality, you can only kill me once. >> san quentin prison in california is home to some notorious killers -- scott peterson, who was sentenced to die for murdering his pregnant wife, laci, is perhaps the best known. but the f