puppy packs

Question
we have nine 3 1/2 month old lab/ chow mix puppies. mom and dad are on site. last night 8 of the pupps ganged up on 1 of the pupps, we have been to the vet and not out of the woods yet with her and the injuries. I was told to seprate them now and not to put them together anymore. is this normal for them to gang up one 1 pup? what causes this? it was the runt of the litter that was really hurt bad. how would you suggest seprating them, there are 6 girls and 3 males. we haven't had anything out of the normal rough playing before last night. i din't know that if they were raise from birth together that this could still happen to this extent. can you tell this was the first litter for us?
any help on this is greatly appreciated. thank you.

Answer
The runt of the litter should have been watched very closely.  It's likely that pup has not received appropriate nourishment and might be underweight and otherwise compromised, especially given the behavior of the other puppies.

Raising puppies together from birth does NOT guarantee anything.  In fact, same sex pups from the same litter often get into trouble later, as adults.  I don't know why you would deliberately allow two of your dogs to produce puppies when you are obviously not prepared to deal with puppies in a knowledgeable manner.  I suggest you give away, with adoption fee of $100, (to reputable homes, do veterinary reference and one personal reference) the remaining puppies and have the mother spayed and the father neutered ASAP.