Ultimately, an act of a dog is the owner's responsibility and it is up to him to keep the dog safe and keep others safe. An aggressive dog charging at you can give anyone a fight or flight reaction. This guy choose to fight. Some of the second guessers may choose to flight. Who can say who is right until we been there ourselves.

Mr. Mellerstig just moved into the neighborhood. So he have no idea what kind of dog he was dealing with. Nor does he know that the dog had an electronic fence device on his collar that obviously didn't work.  All he saw was an aggressive dog charging him and his boy. His reaction I believe is reasonable. It almost sound like he almost empty his clip. That reflects panic and fear as he shot.  I am sure this wasn't the way he wanted to introduced himself to his new neighbors.

Since Mr. Brailey claims he was outside, if  the dog did maul the man or his child, he would sitting in Anchorage Jail right now. Its clear he had no control over the dog.