According to the story, the father caught the man in the process of molesting his daughter, and beat him to death right then and there; I say no crime on the father's part, since he was protecting his little girl.
Now, if the molestation had taken place earlier - an hour, a day, whatever - and the father hunted the bad guy down and took care of him, I can see how there could be a legal problem.
But right now - nope. Not in my opinion.