I'd shoot the dog running at me. If the owner got mad you could just say that the offending dog was about to maul you or your wife. I loved my dog like family. She didn't like other dogs though. When ever other folks visited us we would have to go out to their car & escort them inside before Bear ate them for lunch. If the owner of the offending dog just cried & cried about their dog, be polite. After all, the dog might have been to them what your wife is to you. Offer to help them find a new nicer dog. Like a Collie.
"if you are grown man, there is no dog you should not be able to put down without a gun."
If you think I'm gonna fight a German Shepard or Pit Bull without a gun when I have a gun on me, you belong in a room made of thick rubber.