How many times had your reported the stray/loose dog to animal control or the police over those 4 months?
You say you shot the dog to protect your dog in the your thread title and your family at the conclusion of your post. None of them were in danger at the time you shot the dog. You could have easily retreated inside with your dog and called the authorities.
What was the dog's demeanor/actions that led you to believe it was attacking versus playing or otherwise not being a threat?

