In my opinion, it would make no difference.
If he was molesting the child and the father saw it, I cannot see a grand jury true billing the father under any circumstances. I am not totally sure he only used his hands. That has gone unsaid. One article mentioned hitting him on top of the head.
I agree that the perp should no long waste oxygen, but it does make a difference to me if he was beaten to death after lying there unconscious.
One thing for sure, that creep is never going to attack another child again.