IN 2001, Adrian McCallum helped retrieve the body of an eight-year-old girl who had been buried under an avalanche near Mt Everest.
She was the daughter of a filmmaker who was preparing to document an armed forces assault on the world's highest peak.
She was also Dr McCallum's friend.
From that day, he devoted himself to improving avalanche warnings for climbers, as well as people living in some of the world's highest communities.
Now a lecturer in Geotechnical Engineering at the University of the Sunshine Coast, he is developing an affordable avalanche detection device which, he believes, could have saved lives in the recent Nepal quake.
Dr McCallum admits his life was changed by the loss of his young friend, nicknamed KC, and her parents.
"We were preparing for the Army Centenary Everest climb - I was in the Navy then and was chosen as the Navy's climber," he said.
"We were doing an acclimatisation trek in the Annapurna Sanctuary and film-maker (Squadron Leader) Peter Szypula, his partner Michelle (Flight Sergeant Michelle Hackett) and daughter KC joined us.
"Peter was a part of the team and it was a standard team-building trek, so there was no reason he couldn't bring his partner and daughter along."
It was while the family was hiking through a valley that a massive wall of ice fell from a mountain, crushing them under tonnes of debris.
Dr McCallum and his team rushed to the scene but after two days of digging, admitted the task was hopeless.
"It was an enormous job - a dozen people with climbing axes and snow shovels trying to pick through hundreds of tonnes of ice," he said.
"The Nepalese government sent in rescue teams and our expedition leader decided it was futile for us to continue seaching, so we flew back to Kathmandu."
It was a heart-breaking decision for Dr McCallum, who had forged a close bond with KC during the trek.
"We would walk together, have chats and have our meals together," he said.
"We built up a friendship over that time."
So when word came through that the family's bodies had been found, he returned to the avalanche site.
"I wanted to make sure they were treated with the appropriate respect before they were flown back to Australia.
"I saw myself as being as responsible for getting them home."
But when he rejoined the Everest expedition team, something fundamental had changed.
Dr McCallum's motivation was gone and his priority was to get home to his wife.
While he was committed to the climb, he admits he was happy when bad weather stopped them just 500 metres from the summit.
"I wasn't in the right frame of mind - I'd become disillusioned with mountain climbing. I gave it my all but, ultimately, it was a relief for me when we had to turn back.
"I had a wife back home and I realised life was more important than climbing a pile of rocks. It put humanity and human relationships into perspective for me.
"I decided I wanted to devote my life to helping people and ensuring that sort of thing didn't happen again."
Dr McCallum went on to transfer to the Army and complete a degree in engineering before earning a Menzies Scholarship at Cambridge University.
He specialised in assessing the strength of snow and has since led research projects in the Arctic, Antarctica and the Himalayas.
But his obsession has been to build the radar-based avalanche warning system which is now close to becoming a reality.
The system, which can be made from something as simple as empty coffee tins, bounces radar off mountains to gauge if there is any movement in the ice and snow.
"The beauty of this system, if it works, is that they can build the radar themselves for about $500 and have them permanently set up in these high alpine communities," Dr McCallum said.
"It would empower the local villagers with the ability to monitor their own slopes for avalanches."
Dr McCallum said he was relieved to hear that his friends and colleagues based in Kathmandu survived last month's devastation but believes the full extent of the tragedy is yet to be revealed.
"I think there are still so many stories to be told about isolated communities that have simply been erased.
"But I believe the implementation of a system such as mine in avalanche-prone areas such as Nepal could certainly save tens, if not hundreds, of lives."
Throughout his project, he says KC's memory has remained firmly planted in his mind.
"Back in 2001 I wrote in my diary that I would do this for KC. It's taken me 15 years but it's finally going to happen."
While he hasn't attempted to climb Mt Everest since 2001, Dr McCallum admits he would like to return.
"I am very aware of my own mortality with a wife and three kids but I can't deny that in the back of my mind is the thought that I would like to go back - not just to climb but to see it again."
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