LAS VEGAS (KLAS) — A 55-year-old man died while attempting a rim-to-rim hike of the Grand Canyon on Saturday, according to National Park Service officials.

After starting from the South Rim on Saturday morning, Ranjith Varma, of Manassas, Virginia, was within a mile of Cottonwood Campground on the North Rim when the Grand Canyon Regional Communications Center was notified just before 2 p.m. of a hiker in distress, according to an NPS news release on Monday.

Varma was unresponsive and bystanders initiated CPR before rescuers arrived. A helicopter was dispatched, but advanced life support efforts failed to resuscitate him, NPS said.

A rim-to-rim hike ending on the North Kaibab Trail, where Varma was located, is at least 20 miles with an elevation change of about 5,700 feet. Officials didn’t disclose Varma’s starting point.

An investigation into the incident was being conducted by the NPS in coordination with the Coconino County Medical Examiner.

The Park Service reminds hikers to take care during hot summer months.

“In the summer, temperatures on exposed parts of the trail can reach over 120°F (49 °C) in the shade. Park rangers strongly advise not hiking in the inner canyon during the heat of the day between the hours of 10 a.m. and 4 p.m.,” a statement said.

“Be aware that efforts to assist hikers may be delayed during the summer months due to limited staff, the number of rescue calls, employee safety requirements, and limited helicopter flying capability during periods of extreme heat or inclement weather.”