extreme violent behavior. i'm often curious as to why or how they became this way. but i also think it's a part of the human condition. and i think it's important that people understand that. part of it, i think, is created at birth, but also a big part of it is how one survives in prison. more often than not, a lot of these stories of violence have occurred in the prison setting. in order to survive in such a violent world, most of these people feel they have to be violent. >> in 1992, robert glenn was sentenced to three years for auto theft. when we met him 15 years later at california state prison corcoran, he was still in prison. and two of his former cellmates were six feet under. glenn murdered the first one while he was still in county jail. >> i slashed his throat repeatedly. blood was everywhere. and then another inmate passed me a shank. probably about that long with a