Dead fish. Was told it was from over feeding. was told guts were puked out

Ok here's one. My GF works at a pet store. One of the puffers died. The shit manager said it was because she overfed it. The shift manager said the fish was found dead with its guts hanging out of its mouth. For what its worth the manager is far from a fish expert.

I've searched around. It's been me belief that fish will not eat so much they die from it. Can you foul the water from adding too much food..yes. Is there any concrete information saying a fish will ACTUALLY eat its self to death?

further more what sort of condition might present its self with a dead fish with what apears to have its guts hanging out of its mouth? parasite? I've owned quite a few fish and I'll bet i feed more heavily than anyone. Infact I owned a 6" takifugu puffer..and man That thing would eat untill its belly was round has hell..then it did stop eating and never died from it. I have a green spotted puffer...does the same..doesn't die.

From my understanding is that the fishes digestive system usually speeds up when presented with more food..wich is why they often start pooping when its feeding time. the more you feed them..the less the food is digested(more nutrients in the poo) and vice versa.

Hoping someone has a reliable answer.
I think you have the answer already. I believe that for the most part what you've said is true. I think your GF's Manger is just looking to blame someone, unfortunately.
Sounds more like it tryed to eat something that was to big for it to swallow.
I have seen that happen at the LFS.But a fishes guts wont come out its mouth from over eating.