Not even then.
I agree.
Deserve death? I dare say he does.
But I can't resist paraphrasing Tolkien here:
"Many who live deserve death. But many who die deserve life. Can you give it to them? No? Then do not be so eager to deal out death in judgment."
I don't regard "rehabilitation" (whatever that means) as having any relevance to the issue, one way or the other. If "rehabilitation" actually happens at some point, then that's great and wonderful and all, but it shouldn't be the purpose of any system of justice - certainly not the primary one. The primary purpose should be restitution to and/or the "making whole" of the victims or their survivors, to whatever extent that is possible.
Just to be clear, I don't have any more sympathy for this guy than I do for any other murderous asshole one might care to name.
If he ends up getting shivved in prison (Wisconsin doesn't have the death penalty), I won't shed a tear.
But it's not a matter of whether this particular guy is the "right" one or not. It's a matter of all the other "wrong" ones who will inevitably end up being executed anyway. despite any best efforts that might be made to prevent such a thing from happening. The easiest, most drop-dead, no-brainer way to ensure that that does not happen is to simply forego capital punishment in all cases. Innocent or unjustly convicted people can be let out of prison. They can't be let out of the grave.