My Father Recently Passed Away Monday Night Very Suddenly And

My father recently passed away Monday night very suddenly and unexpectedly.. He did have diabetes and earlier in the day (same day as he died) Came home after the surgery, was walking around, was alert but a little tired. Around 830pm. Said he was not feeling well, and was going to bed, my mom checked on him 15 mins later and was unresponsive. paramedics arrived and were unable to revive him. Hours later at hospital doctor said he had an enlarged heart and had a lot of blood in his stomach. Trying to figure out what may have killed him?..