INYO COUNTY — A man died recently of heat exposure at Death Valley National Park, marking the second heat-related fatality the park has seen this summer, authorities said.

Peter Hayes Robino, 57, of Duarte, died Aug. 1 at Natural Bridge Trailhead, according to the National Park Service.

Bystanders saw him stumble as he returned from the one-mile trail, authorities said, adding he declined help and wasn’t making sense. He then got in his car and drove off a 20-foot embankment, causing a rollover, according to authorities, who said bystanders called 911, helped him walk back to the parking lot and put him under shade.

It took emergency responders 20 minutes to reach Robino, by which time he had stopped breathing, authorities said, adding he was declared dead at 4:42 p.m. An autopsy found he died of hyperthermia, according to authorities, who said it was 119 degrees the afternoon of the incident.

In early July, a motorcyclist died of exposure in the park’s Badwater Basin, authorities said.

Those who visit the park in the summer should stay in or near air conditioning, not hike at low elevations after 10 a.m., drink lots of water and eat salty snacks, according to authorities.