A 65-year-old man was found dead inside his vehicle Monday due to the extreme heat at Death Valley National Park in California, officials said.

A National Park Service maintenance worker noticed the vehicle about 30 yards off road from a highway at about 10 a.m. local time. When the worker walked towards the vehicle, the employee found the man unresponsive, park officials said in a news release Wednesday.

An initial investigation suggested heat-related illness may have caused the driver to run off the road. The man, who is from the San Diego, California, area, was declared deceased at the scene, park officials said.

“The sedan’s tracks ran along the road shoulder and rocky berm before veering further away from the paved road,” park officials said in the news release. “The vehicle did not crash.”