This 2005 photo shows Mount Everest from an aerial view taken over Nepal. (Jody Kurash/AP)

Vinh Truong, an avid outdoorsman with a penchant for danger, had dreamed about climbing Mount Everest for a decade and had been excitedly finalizing plans for months, friends told the Los Angeles Times.

Tom Taplin, a gregarious Californian with a large network of loving friends, had been on the world’s tallest peak for a month, savoring his two great passions: mountaineering and filmmaking, his wife told NBC News.

Dan Fredinburg, a brilliant engineer, adventurer and Google executive who planned to bring the first Street View camera to the top of the world’s highest peak, had “already lived the equivalent of at least 100 lifetimes,” friends said.

Marisa Eve Girawong, an extensive world traveler who had been learning about wilderness medicine in the Everest region since last year, had returned to the mountain that captivated her.

“I can’t think of anything that makes me as happy or peaceful as being out here,” she wrote under an exquisite portrait of the mountain, which was posted on her Facebook page on April 5.

Three weeks later, all four Americans would lose their lives as they endeavored to reach the top of the world. An earthquake-triggered avalanche slammed into hundreds of tents at the base of the treacherous peak on Saturday, leaving at least 61 people injured and a total of 19 climbers and Sherpas dead.

[Before impact, avalanche survivors recall a horrifying ‘tsunami’ of snow and ice]

Despite their deaths, friends and relatives of the Americans said, it’s hard to imagine any of them living their lives differently. But the news was still difficult to fathom.

“To me, there was just no way he could have died on that mountain,” Michelle Fennessy, one of Truong’s longtime friends, told the Los Angeles Times. “He is just such a survivor.”

Fennessy, who met Truong at the University of Chicago, recalled the time the two got lost during a hike in the San Francisco Bay Area.

Fennessy panicked, she recalled, but Truong, who enjoyed river rafting, paragliding and skydiving, remained resolute.

“It occurred to me we might have to sleep in the woods,” Fennessy told the Times. “Vinh just didn’t let it get to him. He was very methodical and very calm, and he just said, ‘We’re going to get out of this.’”

Over decades of mountaineering, Taplin, a 61-year-old from Santa Monica, Calif., also experienced brushes with danger, but he never lost his passion for climbing.

On South America’s tallest peak, Aconcagua, in the early 1990s, he fell into a crevasse and broke his arm, his wife, Cory Freyer, told NBC. He managed to pull himself to safety and eventually wrote a book about the experience. He returned to summit the peak the next year, she said.

Under a YouTube video showing Taplin skiing earlier this year, one of the filmmaker’s close friends posted the following message Monday:

Tom Taplin held SoulSki every year for two weeks skiing with friends in Vail. His spirit brought people together and his wit kept everyone laughing. His camera work always captured the spirit of the moment. Tom died in the Everest avalanche 5 weeks after this footage doing what he loved, shooting a documentary in the mountains. He will be missed by many good friends.

“It sounds trite, but he died doing what he loved doing,” Freyer told NBC.

The same could be said for the 33-year-old Fredinburg, friends said.

Extroverted, humorous and known for his sharp, entrepreneurial mind, Fredinburg was privacy director for Google X, which the Guardian described as “the company’s highly secretive, cutting edge ideas lab most famous for giving the world Google’s self-driving car” and Google Glass.

He narrowly escaped death on Everest last year, when he made it as high as Camp 1, above the Khumbu icefall, and another avalanche struck, killing 16. Fredinburg told the Guardian the experience was “terrifying,” but he decided to return:

Because I took my lead from the Sherpas and they way they handled it, that Buddhist thing. Our Sherpa lost his brother and you could tell how sad he was. And then he said, ‘I must go and tell the family’. And we were like, ‘No, no, it’s too soon…’ And he said, ‘No, I was upset because I was thinking of all the ways in which I would miss my brother but I was being selfish. Because I know my brother is in a better place.’ That way of looking at life really affected me.

His girlfriend, Ashley Arenson, told CNN Money that Fredinburg “was a doer, not a sayer.”

“Going to Everest was a great example,” she said. “He needed to go for himself — to understand his physical and mental boundaries.”

(Here he is discussing his effort to take Google camera equipment to peaks across the globe:)

Garawong, 28, was an avid indoor and outdoor rock climber who had already scaled Mount Washington and Mount Rainier. The New Jersey native had worked in a Chicago hospital was in the process of completing a second master’s degree and postgraduate diploma in mountain medicine at the University of Leicester, according to her Madison Mountaineering biography.

She graduated in 2009 from Rutgers University-Newark College of Arts and Sciences, where she majored in biology and was involved in the Chinese Student Organization, according to USA Today.

Somehow, as the dedicated photographer’s Facebook page revealed, she seemed to be everywhere at once, posting photos from a friend’s wedding in Seattle one day, beside a pool in Morocco a few days later and in France a few days after that. She was as likely to post a photo of herself in an fashionable cocktail dress as she was rappelling down an ice wall at 18,000 feet.

“Thank you for being apart of an amazing year I’ll never forget,” she wrote on Jan 3. “12 countries conquered but 2014 will always be the year I went to Africa for the day.”

In her final posts on Facebook from Everest base camp, Girawong appeared to be reveling in her ascent up the mountain.

“The world is my country,” she wrote, “all mankind are my brethren, and to do good is my religion.”

More reading: 

Massive avalanche slams into Everest base camp following Nepal earthquake

A documentary envisioned Kathmandu’s collapse three months before it happened

Nepal’s earthquake and why Mount Everest should be closed — permanently