Not so sure about that. yes there was proably something else the cop could have done, the dog wasn't just barking it was growling and snarling, probably more just for show, this looks like the kind of dog that even if it did bite you would have been just as scared as you it would have been a nip and then out, not a full on dog attack.
The cop handled it poorly for sure, but i have known others that have shot a dog at large and there is no jail time involved.
In the end it is the dog owners fault, the dog should not be out roaming the neighborhood, someone called the cops on this dog for a reason, obviously his neighbors don't love his dogs and don't want him running loose.
there are leash laws for a reason, it keep other pople safe from your dog and your dog safe from other people.
Just like any other group of people there are good and bad, the people that think everyone else must love their dog because they love their dog are just kidding themselves. Their are a lot of people who would muck prefer not to interact with your dog for any reason. My son is one of them. He was attacked twice by dogs when he was very little, thankfully it was only minor bites. I have to say though even though he is not "afraid" of every dog he sees, he has very little desire to interact with any dog no matter how friendly.