It's possible this could have been Parvo, or it could have been some other cause.
But we all have to be very careful and wary when it comes to buying puppies. Sometimes the breeders are good honest people, but sometimes they're not. To save money and make better profits, they sometimes do not give puppies their puppy innoculations before selling them, yet may say they have done. And of course, there ARE the puppies who have been taken from their mothers much too young. A puppy is ready to leave its mother at about 8-9 weeks old under normal circumstances.
I am so sorry this happened to your little pup.
When you are sick you go to the doctor !its the same with dogs.They need constant care when they are puppies and sometimes when adult.Yes it sounds like Parvo.... all puppies MUST have thier inoculations it is critical as was getting this poor little soul to the Vets to save his life.
Its called duty of care.
How old was he when you got him? Did you take him to the vet when he was sick? What did he say?
Parvo? Did you have him checked out prior to taking him into your home? Had he had his shots?
Cause of death could be attributed to many things.
I'm sorry for your loss.