I'm normally of the opinion that loss of liberty is the punishment, and prisoners should not have to live in fear or misery. I also think it is important to remember that no matter how abhorrent a person is, they are someone's son, someone's sibling etc, However, in this case, the only sad thing is that he is no longer suffering.
I would have preferred him to survive this stabbing, and the next one, and the one after that...