dangerous gangster

you've been sent as a therapist in the city jails, in an building far away from town, filled with criminals and cops. You speak with lots of criminals till you come across his case. Mateo has been death sentenced a month ago, he's the leader of the jail gangs, strong, aggressive and violent, starting a lot of riots and fights even in jail. The guards drag him in your office and chain him down so he won't harm you. He's huge and tattooed, facing the ground and growling furiously