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Americans Asher Burke, Brandon Stapper, Kyle Forti and David Baker died in a helicopter crash on an island in Kenya's Lake Turkana on Sunday, along with local pilot Mario Magonga.

Asher Burke first traveled to a lodge in Kenya six months ago with his girlfriend. The experience changed his life, and he wanted to share it with others.

The San Diego native decided he would try to set up a company offering “ultimate experiences” for globe-trotting young entrepreneurs: people like himself.

The core of the idea was to offer helicopter safaris in Kenya, based around the lodge he had stayed in at Lake Turkana.

Burke returned to Kenya and bought a share in a camping lodge. He partnered with locals, including at a helicopter tour company, and set out to build his dream.

A serial entrepreneur, Burke set out to prove the concept, drawing upon his close-knit circle of friends based in Southern California and from among like-minded acquaintances with a thirst for exploring the world.

Among these were his childhood friends: Kyle Forti and two brothers, Brandon and Brett Stapper. They were joined by another entrepreneur, David Baker, from Coronado, California.

Burke billed the adventures as organic, immediate and intense: flying in small helicopters across the African landscape without a concrete itinerary, stopping along the way anywhere and everywhere participants wanted, to “explore Africa in this incredible way,” Brett Stapper told NBC News.

Brett Stapper had finished his tour with Burke on Friday morning, the same day his brother, Brandon, arrived in Kenya with his wife, Gehane Ribeyre.

“You just get in and take off and start flying,” Brett Stapper recalled. “You just fly and every 15 minutes or so you just get out — on a volcano you’ll stop, on a riverbed you’ll stop — and go and talk with a local tribe that probably have not had a lot of interaction with the modern world.”

He added: “You’re flying over a river and the pilot’s like, ‘Oh, crocodile!’ and he stops and he starts wrestling with crocodiles. I’m like, ‘How do you learn to do that?’ He’s like ‘I don’t know, you just do it. I’ve been doing it for 30 years. It’s what I do. I wrestle crocodiles. It’s normal.’”

Burke and his partners were offering freedom, and the adventure of a lifetime.

The deadly helicopter crash occurred in Kenya's Central Island National Park. Bing Maps

In December, Burke was joined in Kenya by his girlfriend, Emeri Callahan. They spent Valentine’s Day together at Lake Turkana.

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"No matter the day or the place — you’re always the ultimate valentine," he wrote on Instagram.

On Sunday night, the group of 10 — eight visitors and two pilots, aboard two helicopters — had flown to Lake Turkana’s Central Island from their campsite to have cocktails as they watched the sun set over the lake.

But as twilight settled in just after 6:30 p.m., the weather worsened. The group decided to wait, hoping for the wind to die down and conditions improve. They didn’t.