So sorry that this has happened, but nature is a funny thing we once had a rabbit that killed all of her babies but then had another litter and was fine wih them! It has been an awful event for you all,maybe the mum did it ,or maybe the other dog but its hard to accept which ever one it was, hope your mum is not blaming herself too much as awful things happen sometimes.
__________________  From Julie  Alfie  & Lottie |