I personally wouldn't want him murdered. I don't believe in an eye for an eye completely.
I would never wish death on someone as death is what I fear the most myself.
Because he was mentally ill. People's brains work differently.
If he's mentally ill and a threat to society, tough stuff for him.
Plenty of people with mentally ill disorders roaming around, you don't see them going on a killing spree now do you?
Why let him roam around the world, killing people, when his disorder is uncureble? More trouble caused than solved. Let's risk the lives of several people to save one mentally ill one who won't do anything for us in the future except make more trouble.
I know OP can relate to this emotionally because his uncle has the same disorder, but the difference here is, his uncle didn't kill 8 people.