Two men climbing a granite rock wall known as El Capitan in Yosemite National Park fell to their deaths Saturday morning, the National Park Service said.
The agency said Jason Wells, 46, of Boulder, Colo., and Tim Klien, 42, of Palmdale, Calif., fell from the Freeblast climbing route and did not survive the fall.
Park rangers received calls at 8:15 Saturday morning and responded along with search and rescue staff.
Both were reportedly highly experienced climbers.
The Freeblast route is one of the lower sections of the 3,000-foot granite wall.
Climbing.com reports that the two men were roped together when they fell 1,000 feet.
"Tim told me that Jason was the strongest and best partner he ever climbed with," a friend, Wayne Willoughby, told the website, which spelled Tim's last name as Klein.
Rangers are still investigating the cause of the accident.
The pair had climbed El Capitan several times together, and began regularly climbing together while they were in college in San Diego, the website reports.
The site continues:
The "sad news marks the 25th accident resulting in a death on El Capitan. In recent years, Tyler Gordon died on the Nose in 2015 when he hit a ledge after an accident made while rappelling. In 2013, Felix Kiernan died on the East Buttress after being hit by rockfall dislodged by the leader. In 2013, Mason Robison died when a block detached from the Muir Wall and cut his lead line. The first accident by a climber on El Capitan was by Jim Madsen, in 1968, who rappelled off the end of his line while descending the wall to check in on a team on the Dihedral Wall."
The Park Service says more than 100 climbing accidents happen in the California park each year; 15-25 groups need to be rescued.
Climbing.com says the men were simul-climbing, where both climbers climb at the same time. The technique does involve ropes, but falling is still "incredibly dangerous because there is no fixed anchor to take the force of the fall" with this technique.
Almost exactly a year ago, climber Alex Honnold gained the world's attention when he reached El Capitan's peak in just under four hours doing a "free-solo," without safety gear.
Honnold said in 2016 that the rock's Freeblast section "is like a 10-pitch slab," and large sections of El Capitan are "basically like walking on a sheet of glass."