Roger Seheult, MD
I do not know what he died of, but the fact that he sits a lot in one position (racing [real and simulated]), and was coughing up blood afterwards makes a pulmonary embolism high up on the differential. We'll be able to see that on an autopsy. I'd also check for infectious diseases (viruses) as well as that can do it too.
Fox News
BREAKING: 911 audio reveals Kyle Busch was overheating and coughing up blood before his death. According to the audio, Busch was lying on a bathroom floor struggling to breathe and telling others he felt like he was going to pass out. “I’ve got an individual that’s shortness of breath, very hot, thinks he’s going to pass out and is producing a little bit of blood — coughing up some blood,” the caller told dispatchers. | @SandraSmithFox @AmericaRpts