Free roaming canines are a menace to people and livestock and, with all due respect, to think otherwise is nonsense. I live in a suburban area and we have a neighbor who was attacked by two "roaming dogs" in her own carport. One of these dogs was a golden retriever, the other a pitbull. Two dogs together are dangerous, regardless of breed. Pack mentality engages and you (or your birds) don't want to be in the way. One dog on its own is dangerous enough. The "good ol' days" of roaming canines is not a workable solution.
It is sad that the dog had to be shot but that rest solely on the dog owner. It is a shame that because of the owner's irresponsibility this woman was put in the place of having to shoot the dog not to mention the chickens they lost.
Someone had mentioned a "warning shot" to scare the dog. When dogs are in attack mode there is little that will stop them save lethal force. Dogs can be mortally injured and continue to press their attack until they die.
FC, you did what you needed to do, bless you and your brave wife. I know a lot of people would have frozen up in that situation.
Also, thank you for your service in Iraq. My brother served in Desert Shield/Storm and my brother-in-law was deployed twice to Bagdhad an once to Afghanistan.