The local TV station were airing interviews with the dead dog's owner and it so reminded me of interviews with a criminal's mother where she's crying "He's such a good boy. He'd never do anything like this."
The stories I've read said that the owner of the greyhound tried to break up the one sided "fight" but couldn't. He thought his dog was on the verge of being killed so he took what he thought was his last option. I have no idea how the shooting went down (did he have the muzzle against the dog or was he shooting from ten feet way? etc.) or what kind of gun/caliber he used.
The owner of the dead dog has my condolences, but I stand with the greyhound owner.
My neighbors have a wolf hybrid that is very people friendly but dog aggressive. It has been know to get out and attack other dogs but I don't think anyone has filed a complaint or I think they would have had it taken from them by now. Maybe they get a second chance, I don't know how that works. I do know that if it attacks my dog I will not hesitate to kill it.