it comes to the predators we've met inside america's prisons, no one looked the part more than robert g galvin he had a violent streak that earned him the nickname, the phantom. >> they say i'm fast at hurting people, you know, getting people. they'll have holes in them and i'll be gone, you know. like a ghost. >> when i first saw robert galvin, he carried himself in this very tough way, walked luke a wrestler, covered in tattoos, odd hairstyle, shaved his head and had a flap of long hair in the back. and very much cultivated this tough demeanor. tell me about that. >> we considered like a tale, a bulldog tale. it's also called a mongolian. that means warriors. there's warriors or gangsters. we don't have to be told what to do. a warrior knows what to do. >> galvin made it clear knowing what to do inside corcoran meant stabbing his enemies. >> i was on the yard and i stabbed a white guy like 17 times or whatever. from there, they took me to ad seg. and yes, i stabbed another white guy. and that's what got me here. >> galvin's violent ways in prison landed him in corcoran's security housing uni