Why did my Guinea pig die so suddenly?

I remember feeding him his daily dose of carrots last night. This morning I found him curled up in a little ball. Immediately I knew something was wrong because usually he’ll squeak at me. I picked him up and there was diarrhea all over him. He was shaking and his eyes were closed. His fur was puffed up and it worried me. I quickly wrapped him up in a towel and put him near a heater. I called the vet office and ask what was going on. They said to prepare myself because he was passing away. At this point he can’t walk or control his bowel movements. Not even a half an hour later he died. I only had him for two months! He was a baby! It wasn’t time for him to go. I had him caged with another Guinea pig. Will this happen to my second guinea pig? I don’t understand why he died. He was a happy healthy little baby.