The ransom note is still very troubling due to its undeniable strangeness. It has several unlikely details which remain unexplained and give reason for suspicion.
Even if this turns out to be the murderer, I still think something is very fishy in this case. Something to do with the family -- not necessarily the parents.
You know I thought about that and the only explanation that comes to mind is to throw off the cops and pin the murder on the parents so that it would be difficult to find him. The bungling cops fell for it too. It's beginning to make lots of sense now!