With biting temperatures no higher than 20 degrees below zero, and winds that would gust to near 80 mph, the four-man climbing team on Mount McKinley had precious little margin for error. And when they tumbled 300-500 feet down "Pig Hill," suffering broken bones and contusions, that margin quickly unraveled.

Lacking essential gear that would help them survive on the wind-blasted face of the 20,320-foot mountain in Denali National Park and Preserve, and possibly disoriented by their fall, the group's fate was decided by the extreme weather and poor decisions, according to a National Park Service investigation (attached below).

Many of those questionable decisions were laid on the shoulders of Dave Staeheli, a guide for climbing concessionaire Mountain Trip who, according to the investigation, went up Mount McKinley ill-equipped to deal with emergencies, and who was forced by circumstances into abandoning his clients high on the mountain while he raced down for help.

In the end, 38-year-old Beat Niederer of St. Gallen, Switzerland, suffering from broken ribs and without insulated overpants, froze to death waiting to be rescued from Harper Glacier about 100 yards from Denali Pass and roughly 2,000 feet below the summit. Jeremy O'Sullivan, an Irishman who apparently caused the twisting fall when he stumbled while they worked their way down the 30-35-degree pitch of "Pig Hill," somehow survived 17 hours lying on the snow exposed to 70 mph winds and skin-freezing cold. He suffered a broken lower right leg and frostbite that forced doctors to amputate all his fingers, both thumbs, and part of one foot.

Lawrence Cutler, of New York, also suffered frostbite and a strained back, while Mr. Staeheli, a 30-year-veteran of Denali climbs, sustained a broken rib and frostbite.

"It’s the only accident, at least in my career, that I can recall that ended up like this, that ended up an accident involving a guided group, where the guide, because of really no good choices, had to, for his own safety, had to abandon everybody and descend by himself," says Daryl Miller, who recently retired from his job overseeing the park's mountaineering operations and who was called upon to write the investigation's report.

The accident in May 2011 came shortly about midnight on the flanks of a mountain considered to be one of the world's most dangerous to climb due to its proximity to the Gulf of Alaska, which lashes McKinley with brutal storms. Further complicating things as winds increased and temperatures dropped was a lack of equipment that would prove crippling, according to the NPS report.

A decision not to use "snow pickets" -- aluminum stakes that climbers can pound into the snow to anchor ropes -- on their descent of Pig Hill, though not uncommon, left the four climbers roped together and without a solid belay, the report notes. When Mr. O'Sullivan tripped, he pulled the others off their feet, too.

At the end of their tumbling slide the four were scattered across the snow. Mr. Cutler, closest to Mr. O'Sullivan, checked him and determined he had broken a leg while slamming into wind-blown slabs of "sastrugi" snow, a conclusion Mr. Staeheli agreed with. Mr. Niederer was down below those three. As they gathered their wits after the fall, however, the NPS report found that the four never actually huddled together to either assess their respective conditions or agree on how to proceed after the accident.

"Staeheli was unprepared for the consequences of this accident. Once the team splintered Staeheli was no longer able to be responsible for his clients' safety," the investigators concluded.

The brutal weather conditions -- May 11 was one of the coldest days of the month on the mountain, according to Park Service records -- left Mr. Staeheli's right hand so frostbitten that he couldn't use it, and he could "barely hang onto his ice ax with his left hand," the report noted.

The group also lacked critical items that could have improved their plight and possibly saved Mr. Niederer's life, the report found. Though required by the concession's contract the Mountain Trip guide did not have a "spade shovel or snow saw," which could have been used to cut a shelter from the hard-packed snow, or an Ensolite pad that could have been placed beneath Mr. O'Sullivan to somewhat mute the cold from the snow, or which might have been used as a splint on his broken leg, the report added.

Also missing from their gear was a sleeping bag that, while not a contract-stipulated piece of gear the guide should have had, could have been used to keep Mr. O'Sullivan warm. "...(G)iven the extremely cold temperatures found that day carrying a sleeping bag would have been prudent," the report noted.

While the guide did have a bivouac sack that he tried to put around his client, the buffeting winds blew it away, according to the report. While the guide took off his heavy outer parka and gave it to Mr. O'Sullivan, the investigators noted that that "was a humane gesture, but it put Staeheli on a fine line of not being able to keep warm in the increasing wind and cold. He was now in a survival situation and could not walk down slowly with Cutler and Niederer." (As it turned out, winds blew the parka way.)

Radioing for help proved impossible. In a bid to lighten their load so as to make a quick summit, the group had left a second satellite phone at their 17,200-foot high camp; the one Mr. Staeheli did carry to the summit somehow was broken when he tried to attach its antennae after the fall, and other line-of-sight phones they carried either malfunctioned or couldn't make a connection with anyone at the high camp. According to the report, Mr. Staeheli's assistant, who earlier had retreated to the high camp after another client suffered frostbite, didn't have a "Family Radio Servie" line-of-sight phone that might have received the call. Even so, noted Mr. Miller, if they had been able to contact someone the conditions were too severe at the time to launch a rescue.

While the four did have a climbing rope, it was lost while the guide was dragging Mr. O'Sullivan 100 yards downslope from Pig Hill to the "Football Field," a large, relatively flat expanse where a helicopter might be able to land to rescue the injured climber. The loss of the rope "eliminated any chance for Staeheli to provide safety for Cutler and Niederer on their descent," the investigators said.

But there was confusion, too, concerning the attempt by the three to descend to the high camp, with its shelter and potential rescuers.

Cutler said Staeheli asked him to go to the ridge coming off of Archdeacon’s Tower (approximately one third of a mile away across the “Football Field”) where there might be better line-of-sight contact to call on the FRS radio again. Cutler unroped, descended to Niederer, who unclipped from the rope, and the two of them descended to where they had left their packs. They retrieved their packs and continued to exposed rocks on the ridge of Archdeacon’s Tower. Cutler had to help Niederer put his pack on because of an injury Niederer had received in the fall. At the time it was thought that Niederer had dislocated a shoulder and had injured his ribs. Staeheli’s account differs: he stated that he was surprised when Cutler and Niederer descended without telling him. Staeheli had not yet had any contact or conversation with Niederer since the accident occurred. When Cutler reached the ridge coming off of Archdeacon’s Tower he called multiple times on the FRS radio without success. He would continue to make multiple mayday calls on the FRS radio as he descended, but always without success. Much later, while descending the lower half of the “Autobahn” he could hear people talking on the radio, but could not contact them.

There also were slightly differing accounts of what the guide told the two clients as the trio huddled at Archdeacon's Tower while being blasted by winds of 70-80 mph. Mr. Cutler told investigators that Mr. Staeheli had told him and Mr. Niederer that they would go down to Denali Pass where the guide would find a place for them to wait before he continued on alone to the high camp. The guide reportedly also said that for the two men to venture down the Autobahn without a guide would be suicidal.

At this point, the report states, "the situation had become so desperate that Staeheli stated that it was 'effectively every man for himself' and he was 'in doubt that I was going to survive,'" the report noted.

Mr. Miller, during a phone call from Alaska, says the guide faced a no-win situation because he lacked the gear to deal with the elements.

"Without that gear everything unfolded. He didn’t have any choices, everything made the choice for himself. Meaning he was cold after he had given his parka away, and the wind, the wind kills up there, not necessarily the cold. People do very good in 50 below weather, 40 below weather, if they’re dressed right and if they’re moving," he said. "Once you introduce the wind, that’s a whole different thing. He didn’t have any choices to do but more or less just what he did. He had to descend, descend, descend. And I’m sure in Dave’s mind he knew if he didn’t get down alive ... he felt I’m sure that he needed to get help. Because that was his only option.

By 3:30 a.m. the guide had reached the high camp and told his assistant to start a search for the three clients. Amazingly, after 17 hours lying on the snow, through howling 70+ mph winds that drove the wind-chill far, far below zero, Mr. O'Sullivan was able to sit up and wave to searchers in the park's high altitude helicopter the next evening. When a litter was lowered from the helicopter, the Irishman was able to crawl into it. Later that day Mr. Niederer's body was spotted on Harper Glacier, a tiny reddish-orange spec in his parka against the white snow.

In assessing the accident, the board of review pointed to the lack of equipment, failure to work as a group, severe weather, the team's somewhat slow ascent of McKinley, and the communications failures as contributing factors to the outcome.

"Mountaineering guiding companies and guides are tasked with providing for the safety of their clients in a very unforgiving alpine environment. There are objective hazards in the mountains that can injure or kill people that cannot be protected against by even the most diligent practices. Through the use of proper techniques and supervision, a respectful attitude towards the dangers the mountain environment presents and conservative protocols in the decision making process many other dangers can be minimized. A client joining a guided expedition should be able to expect that everything possible will be done to provide for their safety. This investigation team believes that had adequate survival gear, as stated in this report, been carried the outcome of this accident could have been much less severe.

Mr. Miller said the four might have been able to survive a night on the mountain if they had been able to scrape a pit in the snow with their ice axes and huddled together. But that's only a guess.

As for how Mr. O'Sullivan, who at one point tried to crawl partway into his backpack but found it too tight of a squeeze, managed to survive alone, the mountaineering expert has no idea.

"I saw him in the hospital just briefly, for about a half hour, and I told him I was so amazed, that’s a story on itself, the survival," said Mr. Miller. "I would have died. I haven’t talked to anybody I know that could have survived it. How he did I have no idea.”

Traveler footnote: The investigative report contained the following suggestions:

* Guides should be required to carry at least one sleeping bag and one bivouac sack to the summit;

* "A description of the accident should go to each concessioner, emphasizing that guided rope teams comply with the contracts and carry all the mandatory equipment to the summit, including shovels, snow saws, sleeping bags, bivouac sacks, ensolite pads, food and water;"

* "In its contracts, the NPS should replace the wording 'spade, shovel or equivalent' with 'a steel shovel;'

* "At the annual guiding concessioner meeting, a topic of discussion should include 'Turnaround procedures.' The investigation team felt that there were several times during this particular ascent when it would have been prudent to abandon the summit attempt and turn the team back to high camp;"

* "Training for guides should emphasize that, like avalanche victims, leaving the accident scene to call for a rescue is not a viable option on Mount McKinley. The guided party must be its own ultimate resource for the clients on the mountain;"

* "Leaving clients alone, in any situation, creates extreme risk and hazard. Guide training should emphasize that clients, even in an accident must be kept together and their safety ensured."