That's so sad !! I'm far from being a breeder or expert but I've read that because of the C-Section sometimes the moms really don't understand they even had puppies - maybe that's what happened ?  There's more to it but it does happen ....but OMG that has to be just devestating to know your own dog could do this - or worse - to see....
 
My condolences to your son and family - that's very sad.. I hope the mom will be ok.  It's NATURE and please tell them not to hold this against her.  She probably was just very confused after surgery.

