How long does it take for the sheriff to get out to your property? Also, do the owners call the dog back and, if so, how long does it take for them to notice it got loose?
I ask these questions because there may be a way for the dog to be shot without you pulling the trigger. My family had a similar situation, but the owners were not home and the dog in question trapped them in their vehicle so they could not get in the house. They called the cops and, since no one could safely get close enough to the dog to subdue it, they shot the animal. How does this help you? If you're attacked by this dog again, can get to a safe area where the dog can't get you but is still in "attack" mode, and it doesn't take too long for the sheriff to get to your property... well... problem solved. Then the sheriff would notify the owners that he shot the dog and not you. This is a bit of work to go through to get the dog gone... but nothing is too much for safety, in my opinion.