A "history of violence" you say. That sounds bad! But if you look closer a dog is classified as level-1-aggressive if somebody filed a complaint saying they felt "threatened", which can mean anything -- including being barked at. It is not a level-2 or level-3, which are dogs who have actually bit somebody. So you are stretching things quite a bit by saying this dog has a "history of violence". Source: http://www.muni.org/Departments/health/Admin/animal_control/Documents/Codified%20Title%2017%20(54%20page%20PDF).pdf

If this dog were such a beast, then why are his neighbors not saying "good riddance", or "serves him right"? No, they are defending the dog owner because they know this dog was harmless and shooting him was a ridiculous over-reaction by a trigger happy idiot.

And to answer your question I would not shoot any dog charging at me. They always stop and turn away. Be quite the pile of dead dogs if I shot every one that did that.