The deadly accident high on Mount Hood began with one false step by a climber who swept eight others with him into an icy crevasse after a terrifying chain-reaction near the 11,240-foot summit.

Cleve Joiner watched in disbelief as his 14-year-old son disappeared into the void in a flash of steel ice axes, tangled nylon climbing ropes and a spray of wet snow.

"It happened so quick that it was hard to think about what it was like," recalled Cole Joiner, a high school freshman. "I just remember seeing climbers come down at me and then being in the hole."

Two hours later, he was pulled out of the crevasse and quickly hugged his father. The elder Joiner had called for help on a cellular telephone even as he clung to a rope he knew, somehow, was connected to his son.

Three other climbers were dead. The nightmare grew worse when a rescue helicopter carrying six members of the Air Force Reserve crashed near the crevasse, tumbling 1,000 feet down the mountain. All the crewmen were injured, one seriously.

The third and final body was taken off the mountain Friday. The Air Force said experts would be on the mountain within 48 hours to investigate the crash.

But many questions about the climbing accident remained unanswered, including who stumbled. Nearly 50 climbers had registered to climb to the summit of Oregon's highest peak on Thursday, and those involved came from at least three different groups.

The misstep came just after 9 a.m.

Cleve Joiner recalled a line of climbers stretched out in front of him, loosely collected in three groups.

In the top group were four men, two teams of two climbing independently: William Ward, 49, and Richard Read, 48, both of Forest Grove, Ore., and John Biggs, 62, and the Rev. Thomas Hillman, 45, both of Windsor, Calif.

The fatalities were all from this group; only Hillman survived, and his wife, Holly Hillman, said he provided few details of what happened when they spoke by telephone.

"He's just so fuzzy-minded," she said. "He was unconscious for a long time."

But she said another group had crashed into the two Californians.

"That sent John flying down the slope," she said. "Tom did all he could to stop the fall, but the other team got tangled with John and got tangled up in the crevasse."

That description was supported by Cleve Joiner, who said the top group started the chain reaction. He said the four men slid into a group of three below them – a group that included his son – and then swept into a larger group near the crevasse.

Two members of that group were knocked into the 25-foot deep cleft. Joiner and others scrambled to the edge to see if they could help, and Dr. Steve Boyer, a Portland emergency room physician, was swiftly lowered down by rope.

"I immediately went down into the crevasse to help with the decision of who had treatable injuries, and making triage decisions who should come out of the crevasse first," he said.

A Pave Hawk helicopter that arrived a short time later lifted an injured climber off the mountain, returned for another and was preparing to hoist a third aboard when the pilot lost control.

The helicopter veered away from the cluster of rescuers around the crevasse and a crewman released the cable to the waiting gurney, in an apparent effort to avoid further casualties.

"The wind changed, they lost their air power," Boyer said. "I glanced over my left shoulder .... I saw that they were losing power, and I thought, 'Oh my God! They are going crash!"

The chopper's nose touched the snow, it appeared to right itself, and then the uphill rotor dug into the slope. The blades spun off the aircraft, which tumbled down the hill, tossing out four crew members, according to witnesses and videotape of the incident.

"It is a miracle that no one had major injuries," said Boyer.

The accident came just one day after three experienced climbers died on Mount Rainier, Wash. Officials said the three – two of them Oregon State University students – fell near the 14,411-foot summit after they were surprised by snow and 60-mph wind.