What a terrible loss for both families. I live in NW CT and most people here would not run for a gun so much as a phone to call the local sheriff to handle it. But a dog that is killing 17 chickens is not just making one little mistake, it is killing in excess, and would return. My mother has a neighbor whose dog just ran a mile away and killed a free-range chicken, and the owners had to pick it up from the pound. Now they are trying to "train" it to stay in the yard -- no fencing, no leashes. Its ridiculous. The poor dog was hit by a car last year, they are just clueless. All their dogs have always wandered, but this is the first one that has gone and killed something.
I let my own chickens free-range, and if anything kills them, I know that is my own fault, whether it is a car, a dog, or a hawk. I know that their quality of life is better while they are alive, and that is what matters to me.