I can understand how distraught the father is with the thought of the killer of his five year old getting out of prison. IMHO, announcing you are going to murder the murderer of your child is not the smartest move. In some cases, silence is golden.
Maybe he is just really clever. What better defense after the fact than, if I really planned to kill the guy, would I have announced it to the world first?
No, I think it should be made known, especially to the killer. Let him sweat it out.