If I shot at someone's dog regardless of scenario I'd first be looking for the owner on the porch with a rifle. No kidding. You shoot a man's dog around here and he will shoot back. If not, you best get yourself a real good lawyer. Animal rights have taken this stuff nationwide in a heartbeat.
Now, if I'm threatened and carrying I'd pop a warning round first to see the dog's reaction and to get the owner's attention. For now it's the strongest pepper spray or ammonia.
Ahhhhh 50+'ers memories.....we had a rural neighborhood bloodhound that came running for every biker and slow moving vehicle. I'd like to have a nickel for every time we tried the stick or foot method. We would come back with a car and try to door him but to no avail. Then one day we heard someone ran it over. Yeah, poetic justice.