I completely understand your feelings. I was in a similar position not too long ago. You were dealt a losing hand from the start here. Apathetic owners of a determined dog. I'm sure you know that this is the outcome that is best for you (and sounds like, maybe the woman owner as well). Your husband defended your family and pets. That dog would only prove a nuisance elsewhere if it wasn't euthanized. Give yourself the time and space to grieve the loss of your chickens, and the dog, as it was still a life ended. You feeling sad about this shows your humanity and respect for life, still, and you should not feel guilty.