I don't rejoice in the death of the molester, I'm neither glad nor angry... I feel that his death is in God's hands.
As for the father, I don't believe in "justifiable homicide"... The police should always investigate cases like this, which they are and are handing all evidence over to the district attorney who will decide if it warrants investigating by a grand jury. If the police, district attorney and grand jury (if it gets that far) are all satisfied that the father acted out of defense of his little girl and the death was caused far more by the molester's actions... then I don't see a reason to take it any further. This is different than the Zimmerman case where there was no clear reason why someone was killed. The man wasn't just suspicious in someone's opinion... he was actively attacking a little girl.
The father certainly acted in defense of his helpless little girl and was justifiably angry. However, in his anger he did kill a man. We none of us can judge his heart that he wasn't out-of-control. God can, and if he did sin in his anger and did intend to kill the man, then God will judge that.
I say, as long as the authorities believe there is no reason to charge the father with anything, leave both the father and the molester in God's hand and He will judge rightly.