Perhaps numbness? She's the only living connection to the past family left. Sometimes those taught all their lives Christian concepts of forgiveness may go overboard in trying to be forgiving/noble/moving on. Maybe fighting some of their internal emotions, or worn-out, or no longer have a solid base from which to react and come to conclusions, or no idea of how to react to conflicting feelings, or a million other reasons. Grief is just a different mindset that manifests itself in a million different ways.
I have no idea what he is going through, and am not about to judge him or his reactions.
Bottom line, he didn't raise his hands to murder his own offspring, she did.