Here's a topographical map: Link of the hiking trail, unlike what's been said it's not on top of a hill... hills rise steeply on both sides of the trail. And photos taken by the local news shows the area full of smoke a day later, (Carbon Monoxide)... news said the man was found seated, with the baby and the dog, while the wife was found a ways up the trail (as if maybe she was trying to find cell phone reception. And as had already been said by others only a very preliminary autopsy has been done and no results from any toxicology test have been received yet.
(and by the way... Carbon Monoxide is lighter than air (just barely) not heavier, and it flows just like the smoke filling that river basin where the trail follows.
