The heat in AZ in August is at its most brutal, 120+ degrees. The elementary schools teach kids skills like a military survival school in case they get lost. (A lot of small town and suburban homes are literally at the edge of deserts.) And yet this man chose to wander off into the heat. Like you say, he seemed to have chosen to go without the water right next to him.
One of the links mentions a spot of blood on the clothing. Don't know if that's significant, if he might have had an illness or injury.
43 is way too old for a vision quest, at least triple the usual age. Why couldn't he have just chosen to meditate sitting in a country cabin?