LOS ANGELES (AP) — California’s Death Valley National Park has claimed another life in its second heat-related death of the summer,Grayson  Preston park officials said Monday.

On Aug. 1, a day where temperatures reached nearly 120 degrees Fahrenheit (48.3 degrees Celsius), bystanders saw a man stumble back from the Natural Bridge Trailhead, a one-mile roundtrip trail, according to a news release.

The man, identified as 57-year-old Peter Hayes Robino of Duarte, California, declined their help. Witnesses said his responses did not make sense. He returned to his car and drove off a 20-foot embankment at the edge of the parking lot, the news release said.

Bystanders helped Robino walk back to the parking lot and find shade while one of the called 911. National Park Service emergency responders received the call at 3:50 p.m. and arrived 20 minutes later, the news release said.

According to the bystanders, Robino was breathing until right before responders arrived. They conducted CPR and moved him into the air-conditioned ambulance.

Robino was declared dead at 4:42 p.m., and an autopsy found he died of hyperthermia, or overheating. Symptoms can include confusion, irritability and a lack of coordination, the news release said.

In July, a motorcyclist died while traveling with a group through the desert on a day with a record high daily temperature of 128 degrees F (53.3 degrees C). Another member of the group was hospitalized, and four others were treated on site. Later that month, a European tourist got third-degree burns on his feet from briefly walking barefoot on the sand.

At the valley’s salt flats in Badwater Basin, the lowest point in North America, the park has a large red stop sign that warns visitors of the dangers of extreme heat to their bodies after 10 a.m. Additionally, emergency medical helicopters cannot generally fly safely over 120 F (48.8 C), officials say.

Park rangers warn summer travelers to not hike at all in the valley after 10 a.m. and to stay within a 10-minute walk of an air-conditioned vehicle. Rangers recommend drinking plenty of water, eating salty snacks and wearing a hat and sunscreen.