I bet most of us have found ourselves further up the road than we remembered driving, but that doesn’t mean we weren’t seeing and reacting to things, just auto pilot. Years ago I’d seen several doctors (before I got my big gut) telling them I was tired and washed out, get more sleep was the general answer. 
I eventually found a doc’, a big fat bloke who straight away said that it sounded like sleep apnoea (he had it his self). I was given priority as I was driving a semi at the time and got the diagnosis. I’ve now got a cpap machine and haven’t looked back. Who’s to say I wouldn’t have done something similar if I hadn’t got the diagnosis.
I feel really sorry for the family involved and honestly don’t know how I’d cope in their position. Who knows what actually happened ? Does he really not remember it, or is he lying ?