I am so sorry about your son and his dog, thank god they are ok
I would be p****d beyond words.
Stand your ground, contact AC and tell them "I told you about these dogs, and now my son and his dog have been attacked in their own back yard." Write an officail letter of complaint, cc it to the police, the county commisioners, the AC and the media.
Ima, needs to face up to what he is doing and needs to be called to book.