On Good Friday, April 18, Mr Brooks Entwistle was up before dawn when he heard the usual groaning and rumbling of glaciers breaking.
From his tent at Everest Base Camp, he had a spectacular view of the Khumbu Icefall, which climbers scaling the world's highest peak from the south side must pass, at great risk.
The Singapore resident had hiked through it once the previous Tuesday, being among the earliest groups to set up at base camp, and there was a sense of optimism among him and his Sherpa guides that it was a good route up this year - going up the middle rather than the more treacherous left side.
"I was up to look at the icefall. I heard it first, then saw it," said the 46-year-old of the deadly avalanche that struck at 6.30am, killing 16 Nepalese guides and porters in the worst tragedy on the mighty mountain.
Nearly 340 climbers were permitted to scale Everest this year, each paying between US$35,000 (S$43,900) and US$100,000 to attempt a summit within a three-week May window.
"It wasn't clear at the time how significant it was because every night, there are always avalanches in the canyon where you are."
That morning, Mr Entwistle's team was supposed to hike through the icefall at 3am to the higher Camp 1. Climbers cross it quickly in the wee hours of the morning when the ice is frozen and thus less susceptible to shifting.
Mr Entwistle describes it as "an amazing adult ice jungle gym". "There are ladders up and across and it's always different. Ice is always shifting and the 'ice doctors' are always putting new ladders in, taking them out, and sometimes ladders break."
The guides and porters, including the 16 who were killed, were hauling up loads. But Mr Entwistle's climb was postponed for a day as the porters had not properly set up at Camp 1.
By 7.30am, it became clear it was serious. Radios were going off, crew members were climbing up to help with the rescue and the helicopters started moving in.
Mr Entwistle's climbing guide, 26-year-old Kancha Nuru Sherpa, had come down from Camp 2 and had passed the group of 16 Sherpas. "He came back to camp and was first person who told me, with a look in his eyes I'll never forget: It's not five or six. It's 15 or 16," recalled Mr Entwistle, who retired from his job as chairman of Goldman Sachs South-east Asia and CEO of Goldman Sachs Singapore last year.
By late morning, 13 helicopters came in, one by one, lifting the bodies from the icefall.
"That juxtaposition of the red helicopter, the long wire and the limp body against the blue sky with the Everest west shoulder - no one there will ever forget that," said Mr Entwistle, who returned to Singapore last week.
"At that point, no matter where you were, what you thought of the incident, you knew it was an unspeakable tragedy."
The next morning, he watched the first group of Sherpas hike out. They were from an expedition team that had lost five guides. Mr Entwistle's own team from the American trekking agency International Mountain Guides also sent their Sherpas home that day to grieve and be with their families, with the understanding that they would return on Tuesday night.
"The emotion was, they'll come back and the climb will still be on. I hadn't come to the realisation that the mountain closing was on the cards."On Easter Sunday, rumblings started of a group of Sherpas who had come together to make some demands on the government, and there were rumours of tension and talk of threats that if any Sherpa were to climb the mountain, he would be given trouble.
The turning point came on Monday, when the climbers and guides at base camp attended a memorial service for the dead Sherpas, which, to Mr Entwistle's surprise, turned into a political rally.
The guides issued a manifesto, asking, among other things, that the government channel 30 per cent of climbing fees it collects - US$3 million this year - to a mountaineering relief fund. They also wanted death compensation to be doubled from the current one million rupees, and increase medical and life insurance payouts.
By Wednesday, after his team's Sherpas came back and had a meeting with the expedition leader, the news was given to Mr Entwistle and his fellow climbers: It's over. His team was the largest with 80 Sherpas, and they were not willing to continue climbing. The other companies followed suit.
Thursday morning marked the mass exodus: As many as 15 helicopters were hovering above in the Everest sky, waiting to pull climbers out.
The climbing community has rallied around the Sherpas as they negotiate with the government. Several fund-raising drives are going on, including one by the American Alpine Club that has raised more than US$50,000.
Mountaineer and leadership coach David Lim, 49, who led the first Singapore Everest expedition in 1998, said a "common voice from the Sherpa community" will emerge. He expects that climbing will continue next season, but with enhanced insurance coverage for the Sherpas, and stronger engagement between them and the government.
In the longer term, Sherpas, now better educated and trained, will have a more equal voice in expeditions.
"As the icefall presents a continuing hazard, and commercial concerns are still often dictated by foreign companies, an uneasy tension will continue to exist. Managing it well is both a leadership skill and art," he said.
Mr Entwistle believes climbers may now migrate to Tibet to try to scale Everest from there. But he does not know if he will return to the mountain.
"I worked hard; I wanted to climb Everest my whole life,” said Mr Entwistle, who grew up climbing mountains in his home town of Colorado and has scaled several peaks, including Mount McKinley in Alaska, where he was caught in a devastating storm. He took nine months to prepare himself for Everest, working out six days a week and doing training treks.
"But I've never questioned the call to honour the Sherpas and respect that the mountain needs to close and grieve for a while."