In heatstroke, you may find cerebral edema, visceral petechial hemorrhages, subendocardial hemorrhages, and hepatocyte necrosis. Depending on how recent the deaths and how long the exposure pre-mortem.In that link, it appears there's an eyewitness who encountered the hiker and tried to give aid, and called 911.
Or perhaps the man called 911 himself, and the 911 operator interviewed him. But by the time LE got there, he'd died.
Whatever the interactions before he died, the hiker apparently didn't complain of being attacked, bitten by a rattlesnake, drinking bad water, having chest pains, etc. He'd have spoken about his symptoms and behaved as though he was experienced heat exhaustion/stroke.