I remember your post not long ago and I'm sorry for the decision you had to make. It is extremely hard to have to rehome your dog, they are usually indoor pets so play such an integral part in our daily lives. It is not something I would deal well with, having to make the decision between the animals and the pet.
There is something about the kill instinct that has a way of manifesting in random dogs. So many dogs are able to maintain, but some get the switch flipped and it seems impossible to turn it off. I'm sure it's possible but it doesn't seem like it in the moment.
I am beginning to think this was a "drive by" and they may not return, since now I 'm ready for em....