My brother-in-law spent his entire career in the Chicago juvenile justice system working with violent offenders, mostly gang members. They had those same dead eyes and he said most of them would kill him just as easily as shake his hand. He didn't believe in rehabilitation and he said that by the time they were old enough to get to him (which is a lot younger than that girl) they were already lost.
Now that he is retired he spends his time gardening, fishing and avoiding other people as much as possible. The end result of a career spent with the worst humanity has to offer.