I agree, however, this will not happen ... so, I would like him to live a very long and painful life behind bars. A life without freedom, a life without any future except prison, a life without a chance of seeing sunlight other than that seen through concertina wire.
Then death via old age and the awaiting hell that is his reward.
The problem is that also will not happen. He’ll be paroled in 7 years and he’ll get out and kill again.
I’d just put him in the general population and make sure all the other prisoners know exactly what he did. And, each time he enters the compound, all the guards pointedly turn their backs.