The sound of a rock climber falling from a cliff cut through the black, cold silence of the early morning hours in Yosemite National Park.

World-renowned climber Alex Honnold could not see the commotion above him, but he could hear the sound of a body banging into jagged rocks, and it gave him a picture of what was unfolding.

His climbing partner, Emily Harrington, of Colorado, had slipped on the first pitch, or segment, of what was planned as a daylong ascent of the granite face of El Capitan on Sunday.

“It’s hard to say for sure what happens in the dark,” Honnold said Tuesday, talking by cell phone as he climbed a cliff in east San Diego County with his girlfriend, Sanni McCandless.

Honnold, who had supported Harrington’s attempts to free climb the challenging Golden Gate route up the sheer rock face in a single day, leaped into action. He put tension on the ropes he had been holding to support Harrington and ensure that she did not fall off the cliff if an accident occurred, a technique known as belay.

After “catching” Harrington, Honnold, the star of the 2018 Oscar-winning documentary, “Free Solo,” helped lower her to a safer location. Then he handed the rope to another member of the support team and began climbing.

“It made sense for me to climb up,” Honnold said.

He scrambled up the rock wall to reach Harrington, a renowned climber in her own right.

“She hit her head pretty hard,” Honnold said. He said he does not have emergency medical training but he did what he could to immobilize Harrington’s back and neck as a precautionary measure.

Then Honnold and the support crew called Yosemite Search and Rescue for help. Honnold said he told stories to distract Harrington and to keep her awake during the two hours they waited for the rescue team to arrive.

“I wanted to make sure she knew who she was and what was happening,” he recalled. “And then it was a matter of just waiting.”

Harrington, 33, a five-time national champion in sport climbing, was taken to a hospital in Fresno, Honnold said. In an Instagram post Monday, Harrington reassured people she was not seriously injured.

“I had an accident yesterday on El Cap. I’m banged up but gonna be OK thankfully,” Harrington wrote. “Not much to say except I took a bad fall and pinballed a bit then somehow hit the rope with my neck.”

She thanked her support crew and Yosemite Search and Rescue, known as YOSAR, for getting her off the wall.

The plan had been for Honnold, McCandless, who was with Honnold at the bottom of the climb, and a few others to support Harrington as she made her way up the 3,200-foot vertical face of El Capitan, one of the world’s most challenging climbs.

Harrington’s boyfriend, Adrian Ballinger, of Lake Tahoe, was waiting higher up the face to support her final pitches to the top.

“It was complicated logistics because climbing El Cap in a day requires a bit of a plan,” Honnold said. He knows this firsthand: Years ago, he nearly died on Half Dome when he went off-route.

Ballinger, known for guiding climbers on Mount Everest, did not immediately return a call on Tuesday.

Harrington had successfully free-climbed the Golden Gate route over five days, camping on the rock, Honnold said. But she wanted to complete the climb in one day, which is “pretty hard,” Honnold said. “It’s only been done a couple of times.”

Free climbing is a method of rock climbing that uses ropes only to protect against injury during falls and not to assist a climber’s progress. Honnold is known for being a free soloist, a purist’s version without the safety net of ropes.

Honnold said in May that he wanted to support Harrington’s climb because she had assisted him in some of his previous ascents. Scaling El Capitan on the Golden Gate route was a big challenge for Harrington, who failed to complete the route in a single day in the few times since May, Honnold said.

“It would be a big milestone to feel like she had improved as a climber,” he added. “She knows she could do better. Not prove anything, but it’s nice to see a progression in your own climbing.”

Honnold said he had seen accidents while climbing but had never been directly involved in a rescue effort until Sunday. He said the incident has prompted him to consider taking emergency medical classes to be better prepared, in case he is faced with another accident.

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‘Free Solo’: El Capitan climber Alex Honnold on risks, love and thoughts of death But, he added, the episode underscored how safe climbing is when it is done the right way.

“Everything worked the way it was supposed to,” Honnold said. “She was climbing with safety equipment, and it caught her. The reason she is going to be totally fine is because we were using safety techniques.”