> I cannot help but think that the cruel punshment did indeed work.

I struggle to understand how you reach that conclusion. Occams Razor would suggest that one only need to assume that a thirteen year old might only need to grow p for this outcome to be plausible.

> If he was given a shorter sentence without solitary, he would probably make friends with other prisoners and continue shooting people after he got out od the prison.

Or, hear me out here, if you put the prisoners in a situation where they are able to learn behaviours that reinforce social norms rather than jamming them together likes rats in a cage guarded by sadistic lab technicians, then you probably would have lower recidivism rates. This is what the data says, when comparing the conservative penal systems in the West (with rates of 50%+ after 2 years) with progressive states (with rates around 20-25% after 2 years).

It turns out not treating people like monsters means you have fewer monsters.