Likely some kind of drug medication involved. Could have been something like a low sugar level even.
I would say you’re probably right on with your assessment. They are quick to say it’s not drugs or alcohol suspected, so that makes me think there was something they could clearly tell was physiologically based. Maybe even perhaps some kind of a stroke or seizure? Like you said though - low blood sugar/insulin overdose, etc.. could be a possibility as well.
It will be interesting to hear what the *official* story is.
Or a stroke, maybe a slow bleed.
Was he the only one in the vehicle?
If he's diabetic, probably too much insulin and not enough food.