Death of Shih Tzu pup

Question
My friend got a pup (supposedly AKC registered for $750) from a breeder that told her the dog would only reach 5-7 when full grown.  The standard for this breed is 9-16 lbs.  She got the pup at 10 weeks on a friday.  By the next day it seemed ill and by Sunday we rushed it to a vet hospital where they put it in an incubator with oxygen but it died a short while later.  Symptoms were: diahrrea, drooling, foaming at mouth, listless, distended stomach, lethargic.  They are performing an autopsy but nothing yet.  They have ruled out, parasites, worms, etc.  What do you think happened?

Answer
I really hate to speculate because it could be anything from rabies to parvo to distemper. There is really no way for me to know. Just wait on the necropsy (autopsy) and see what the findings are. Most reputable breeders should work with you in situations like this and you may be able to get a refund or another pup. If it turns out to be genetic defects or a contagious disease contact the breeder as soon as possible to have the litter mates checked out before the disease can have a chance to spread to other animals. Hope this helped.