A record-breaking US rock climber plunged 305 metres to his death off a Mexican mountain on Wednesday – after choosing not to tie a knot in the end of his rope that may have saved his life.
Brad Gobright, 31, was rappelling down the sheer El Sendero Luminoso rock face at El Potrero Chico, near Monterrey, when he tragically slid off the end of his line.
He had been descending the renowned cliff with Aiden Jacobson, 26, when he reportedly misjudged the length of rope he had left beneath him, according to The Sun.
Jacobson, who was sharing the 80m rope with Gobright for the simultaneous rappel, also fell but miraculously survived after landing on a bushy ledge on the 762m cliff.
Describing the harrowing moment they both began falling, Jacobson told Outside: "I was on the left. He was on the right.
"Then all of a sudden I felt a pop and we started dropping. It was basically a blur. I screamed, he screamed.
"I went through some vegetation, and then all I remember is seeing is his blue Gramicci shirt bounce over the edge."
Tributes to well-known Gobright have come in from across the climbing world.
"The climbing world lost a true light. Rest in peace," wrote Alex Honnold, focus of the Academy Award-winning Netflix documentary Free Solo.
"He had a magic about him on the rock, unlike anyone I've ever met," added Alice Hafer, one of Gobright's regular climbing partners.
"He was so supportive and encouraging, always pushing me harder and believing in me."
The pair had misjudged how much rope was left beneath them, according to Jacobson – who was left with only a broken ankle from his fall.
They were using the technique of simul-rapelling, by which two climbers abseil on opposite strands of a rope and act as counterweights to each other.
That means that if one climber falls off the end of the rope, the other climber loses their counter-weight and also falls.
The chances of that happening can be minimised if knots are tied in both ends of the rope, but Jacobson said that they had chosen not to do that.
One reason climbers may choose not to do so is that knotted ropes have a higher chance of getting stuck when the climbers, after abseiling, pull the rope down.
Gobright abseiled off the end his side of the rope, causing Jacobson to also plunge, according to the surviving climber.
Mexico's Nuevo Leon state civil defence office said Gobright fell about 300 meters.
Gino Negrinni, a Costa Rican climber who was on the mountain at the same time, said he heard the climbers' chilling screams as they plummeted, according to Rock And Ice magazine.
Gobright is believed to have landed near the bottom of the cliff on a ledge known as Skull Amphitheatre, according to the mag – which hailed him as "one of the most accomplished free solo climbers in the world."
The veteran climber, of Orange County, California, had been scaling cliffs since he was seven and held multiple speed ascent records.
Among his biggest achievements was his October 2017 speed record for ascending the Nose route of El Capitan in Yosemite National Park.
That climb is considered one of the world's most technical and dangerous in the world.
He and climbing partner Jim Reynolds raced up the nearly vertical, 884m rock face in just two hours and 19 minutes.
Previous record holder Alex Honnold wrote an emotional tribute to Gobright, saying the climbing world had lost a "true light".
He wrote on Instagram: "I suppose there's something to be said about being safe out there and the inherent risks in climbing but I don't really care about that right now.
"I'm just sad for Brad and his family. And for all of us who were so positively affected by his life. So crushing.
"Brad was a real gem of a man. For all his strengths and weaknesses (like his insanely strong fingers, or living out of a Honda Civic …) at the core he was just a good guy."
In a statement, the state civil defence office said: "We extend our sympathies and support to the rock climbing community."