Linda, that is heartbreaking - I'm sorry!
This actually reminds me of Diggy4's story (Paula) a bit ago - bc her babies became suddenly and violoently ill with same symptoms - and turns out it was clostridium, likely caught from an infected Bully Stick. HGE is often caused by clostridium (which can kill overnight) - so it makes me wonder if the friend happened to give the pup any form of treat - it would be something to look into for them, if appropriate. (?)