If the dog comes back, get rid of it. Bury it and forget about it. And don't tell a soul (other than deaconjim of course). If anyone asks, just say there was a problem at your house too, with animals being attacked/killed but whatever hasn't been back.
That's why I suggested giving him the opportunity to deny it was his dog. That way when she blows him away the owner can't come back that she shot his dog. If I shot him though there would be no dog.