I carry a gun....and will not hesitate to use it if a pitbull attacks my dog.
I had to do that once. It was a loose pit bull with no owner around. It had broken out of its backyard fence. It had my dog by the neck in its jaws and was shaking him violently. The Pit bull had the mass of a bag of concrete mix, so I could not budge it. Took two shots to get it to drop my dog.