With Shaheen Baig out of the picture, fixing the ropes fell to half a dozen other loosely organized climbers who’d learned their skills on Everest, where the presence of so many less-experienced climbers requires fixing ropes on every inch of the mountain. At some point, after they'd begun setting the route at the Bottleneck, they were joined by Spaniard Alberto Zerain—the fastest climber on the mountain, but not part of the advance team—who’d climbed straight through from camp three. Without Baig to direct them, the group wasted line on the low-angle slopes below the Bottleneck and ran out of gear well before the crux. When van Rooijen, who'd set out with the other climbers on their summit bid, arrived around sunrise, he and the others were astonished to find Zerain already there, directing the route setting.

"We had discussed this so many times," he recalls, "what had to be done and who had to take care of this job."

The Bottleneck soon lived up to its name.

Klinke, stuck behind at least 20 climbers, began removing ropes from the lower slopes and passing them up the line. "There was no way we were moving fast enough to summit and get down before dark" he says. "Accidents on K2 happen when people spend too long on their ascent."

Most climbers aim for a time of 10 to 12 hours between camp four and the summit. This year, nobody reached the top in less than 16 hours. Klinke and his teammates, Eric Meyer and Fredrik Sträng, turned back for camp four at about 10 A.M.

The first fatality occurred shortly thereafter, in the Bottleneck. Dren Mandic, a Serbian climber who unclipped from the rope to adjust his oxygen equipment and pass another climber, lost his footing and fell onto Cecilie Skog. The rope stopped Skog, but Mandic tumbled hundreds of feet.

Meyer and Sträng left camp to help but, on the way, received radio communication that Mandic was dead. When they reached Mandic's corpse, hours later, his teammates were trying to lower the body back to camp four. The recovery went wrong almost immediately. Jehan Baig, a Pakistani porter working for the Serbs, toppled onto Sträng before sliding headfirst down the slope. He made no attempt to arrest his fall with his ice ax and tumbled off the mountain. The remaining climbers left Mandic's body and returned to camp four.

Up in the Bottleneck, Pemba Gyalje Sherpa, from the Dutch team, was spooked by the accident and the late hour. He advised the climbers to descend, but Marco Confortola gave a pep talk, noting that the first climbers to summit K2, in 1954—Italians, like him—did so at 6 P.M. They all continued up.

Zerain, climbing solo ahead of the pack, topped out around 3 P.M. and descended so quickly to camp three that he didn't learn of the disaster until the next day. At 5:30 P.M., Lars Naesse summitted with the Norwegians, followed within half an hour by Skog and Chhiring. Five Koreans and two Sherpas working for them reached the top at 5:40 and, according to Pakistani officials, spent 90 minutes there. Just after 7 P.M., about an hour before sunset, Van Rooijen, McDonnell, and the rest arrived. All but Cas van de Gevel, of the Dutch team, had started down when Confortola arrived between 7:30 and 8 P.M.

ROLF BAE WAS DEAD. The icefall that killed him also took out crucial fixed ropes on the upper mountain. Skog, Naesse, and the 14 others strung out behind them would have to descend the Traverse and Bottleneck in the dark, with only fragments of ropes to clip into.

After the disaster, several news stories noted that the climbers were "stranded" above the Bottleneck. In reality, the Traverse and the Bottleneck are entirely navigable by an experienced climber with the right equipment. Many earlier expeditions to K2 didn't rely on fixed ropes at all. Instead, climbers tackled the peak alpine-style, ascending and descending while roped only to their teammates. But alpine-style climbing on terrain this steep requires two ice axes, in the same way ice-climbing does. Most of the climbers in August had only one tool each, which made climbing down the dark, debris-strewn slope that much more insecure.

After the initial accident, Naesse removed a short rope he carried in his pack, and he and Skog crept over the icy rubble and descended into the Bottleneck. Higher up, the climbers were still unaware of the icefall. Above the Traverse, Cas van de Gevel came upon Hugues d'Aubarede, sitting in the snow, exhausted. The porter Karim Meherban was missing and would not be found. Van de Gevel passed the Frenchman; soon after, he heard a crash and turned to see d'Aubarede falling into the void.