We all can "monday morning quarterback" this scenario.
We were not the victim. We were not there. We may not know all the laws of that State. And we also may not have the ability to spend hundreds of thousands of dollars in a criminal defense trial.
That said, even against a person with "connections" etc,, it's wise to do as much as possible to avoid shooting another person. Even if you are armed,, and that person isn't.
Yes,, extenuating circumstances (age, health issues, aggressor bigger, out in a public street, etc) can help defend your side in court. But it's MUCH easier to prove a self defense case if you do as much as possible to avoid a lethal response.
Just like Sam mentioned above,, he had (2) situations where an aggressive type created the problem. No, he wasn't physically attacked,, but he chose to USE the LAW to get this person in trouble. AND,, by doing so,, if that person had chosen to make a 3rd attempt,, AFTER a court found him at fault,, then Sam would have a SOLID history of trying all he could to prevent it, and was forced into a lethal confrontation.
Yes,, the physical attack is a bigger issue.
But going back to my first part,, "we were not there" and I wonder, did the victim of the assault remain totally silent after the dog got into the street? Most humans can not keep their mouth shut. And if the aggressor came out of his house,, swearing etc,, most people would say SOMETHING in response. Yes,, trying to retreat is what should be done. But we have been presented with a side of a story where the victim has only expressed calling the dog, loudly. What else was said or exchanged?
My point is,, we were not there,, and as Paul Harvey used to say; "The rest of the story" is not known here. Remember,, a jury is a 3rd party, and they will be called upon to look at things AFTER the actions, and can only pass judgement based upon facts presented.
I'd prefer to have a lot more facts to back up my side of things if I were on trial for killing anyone.
Personally,, if it had been my dog,, and he came into the street,, I would have gotten him and retreated,, AND not allowing anybody to get behind me. Avoiding the "attack from behind." If I could have,, I would be holding my dog by the collar,, and keeping the dog between myself & the aggressor if possible. And by backing away,, while facing a potential aggressor, I can use that to avoid the physical attack possibly.
Many of y'all may remember,, a few years ago,, I had a guy come out of the woods, come between my truck & my wife's car, and attempt to get in. I had my firearm,, but I didn't shoot the guy. I did as much as I could to stop any potential assault or whatever without shooting him. By that person's actions,, I could have possibly shot him & eventually gotten away with doing so. But not before a serious legal case that could have destroyed my life. (And 2 different cops from 2 different depts said they would have shot him.) Do all you can to avoid the killing of anybody. Make the shooting of someone the very last resort if at all possible.
Small disputes can escalate into a very serious problem quickly. Locally, we had a case in the last week or so,, where a teenager was shot by a landowner. Apparently the teen had parked on the landowner's property, and a dispute happened. The landowner is in jail, facing manslaughter charges.
We as responsible firearm owners need to be as careful, and as calm as possible when faced with the potential for escalation of a problem, and do all we can to NOT shoot someone.
But again,, I wasn't there,, and I do not have enough facts to make a decision one way or another about what the OP has put forth.