Sad to say, but you won’t get around to killing him, no matter how frightful his crime. He’s 17 and 5 of the 9 members of SCOTUS have declared executing anybody who was under 18 when he committed his crime is cruel and unusual punishment. That’s why the GOP must win this election.
Prison, hard labor for the rest of his life, 23 hour lockdown.
Not only is he not eligible for the death penalty, but even if they try him as an adult (they almost certainly will), he cannot receive a mandatory sentence of life without parole. SCOTUS has ruled on that point too, as I recall. But they can certainly put him away for a good forty or fifty years.