In cases like this and things such as mass shootings with eye witnesses where we know without a doubt who has done it, it's hard to argue that these people deserve to live.
It isn’t a case of ‘deserving to live’ though. As it happens I don’t think they do deserve life and the privileges that life brings us.
But we as a society do not deserve to be put in the position of killers. And we don’t need to be. We can just lock them up, and it could be for life.