Why Did My Dog Die So Suddenly?

My nearly 11yo Schnauzer left us last night on the way to a 24hr vet. Before passing, his tongue was out, he drooled, and dry heaved in the car. 15 minutes prior he seemed largely unresponsive to our calling other than panting.

These last two days hehad been vomiting 5-7x a day, he couldn't keep food down. He had a complete loss of appetite ever since the night two days ago. I had to stuff food down his throat with my fingers as the vet said he needed food to take his medication (NSAID for a leg injury, appetite enhancer, omeprazole).

A month back, vet ruled a torn ligament on the hind left leg, bones were very healthy via X-ray, blood test showed fully functioning liver, kidney etc. However, after the left leg looked nearly healed, his right leg acted up and he started limping again.

The visit to the vet two days ago indicated very low heart rate (48, compared to 70-100 of a normal dog), previous visits a month ago were said to be normal heart rate.

He has a history of (chronic) pancreatitis and we thought this could be related but doesnt seem like it now. He also has a growth near his spleen / liver that we decided not to test for 4 years ago.

He was a very healthy looking boy and was in better condition than many of his same aged peers when we visited the vet for his vaccination two months ago. This all happened so quickly that I cant believe its real. I thought I could still feel a shallow heartbeat but the vet said his heart stopped beating before we arrived.

Im sorry if this was too much information, but Id like to hear the possible reasons from different people in the community as the vet did not provide any cause of death for my baby boy.