I can't say I agree that "most" support the death penalty but I will say this..
killin's to good for em. And here's why I say that.
If you're an atheist, then there is no hell and therefore, no punishment;

If you're a christian, there is the chance that shitheads like this may find redemption at the last second and end up in heaven, again, no punishent;
(and isn't it amazing how so many of them, usually right before their parole hearings, find Jesus in prison? Would that the churches could have that many converts who have seen the light.)

If you believe in reincarnation, then somehow the prick will come back, and who wants him back in any form.

If you're a heathen like me, then there is no way to know what will happen in the afterlife, assuming there is an afterlife,

Punish him now by letting him rot in a 4x6 cell for the rest of his days...no cable tv, no weight room, no work release or chain gang, no steak and potatoes, no therapy...plenty of time to think about his actions and suffer in silence. and the cost would be minimal to say the least. I suppose we could toss him a book from time to time and hose him down once or twice a week.