DO NOT DELETE OR BLOCK HIM YET.

You want all the evidence you can on him. You need to get some screen prints done of what this boy has been saying. Try and get the friend to do it if your son cant.

The more chance this kid has to stuff up the better it is for you guys IYKWIM. Kind of like keep your friends close and your enemies closer.

After this has all gone through court then do all of the above with blocking, etc.

In a way in cases like this you really want this boy to say something incriminating himself and then have evidence of it.