Americans Asher Burke, Brandon Stapper, Kyle Forti and David Baker died in a helicopter crash on an island in Kenya's Lake Turkanaon 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 girlfriend, 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.
In December, Burke was joined in Kenya by his girlfriend Emeri Callahan. They spent Valentine's Day together at Lake Turkana.
"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.
"He had the greatest soul and he had the greatest love for humanity. This wasn't an ordinary man."
By 8 p.m., the light was gone, and the group was concerned they would be stuck overnight on the island.
They made the decision to go for it: It was only a 15-minute flight back to their campsite.
A group including Callahan, Ribeyre and two others — whose identities have not yet been made public — got in one aircraft, piloted by one of the partners in Burke's project.
The four friends — Burke, Brandon Stapper, Forti and Baker — got in the other, piloted by Mario Magonga. Only one of the aircraft would make it back safely.
According to the Kenya Civil Aviation Authority, the two helicopters took off just after 8:30 p.m.
Only a few minutes later, the aircraft carrying Burke and his friends disappeared into the darkness.
The other one landed safely in Lobolo Camp in the town of Lodwar.
"They were aware they lost contact, but weren't sure [Burke's helicopter] had crashed," Brett Stapper said. "They called me, saying they needed search and rescue. There was nothing around. All they had was a sat phone."
Stapper sprang into action, and with the help of some well-connected friends was able to get the Kenyan military mobilized to search for the missing aircraft.
"We were hoping for survivors," he said.
By 3 a.m. on Monday, rescuers had located the wreckage. No one had survived the crash.
"He was my best friend," Brett Stapper said of his brother, Brandon. "It's kind of just been him and I for 18 years now. We do everything together. We used to talk every hour of the day, basically."
He described his brother as "the core of the community," adding: "Him being gone is like a huge hole in all of San Diego."
Kyle Forti, who was living in Colorado Springs, Colorado, was the oldest of eight siblings and was the co-founder and partner of a political consulting company called D/CO. He and his wife, Hope, were expecting their second child, according to his mother.
"He had the greatest soul and he had the greatest love for humanity," Ann Forti said during a phone interview Monday. "This wasn't an ordinary man."
Hope Forti wrote in a Facebook post that she wanted people to remember him "primarily as a husband and father."
She added: "His biggest goal was to be a stay-at-home dad."
Richard Bailey, the mayor of Coronado, wrote that Baker would be missed "terribly."
"Dave was an amazing family man, businessman, and adventurer," Bailey added. "He had an infectious laugh and made friends wherever he went. Dave lived life to the fullest."
Omondi Jakano, who was a friend of the pilot, said Magonga would be remembered as "a strong man in mind and spirit, a specimen of intellect and a great sports fanatic in school."
Burke's family recalled how he had described Kenya as "the closest thing on Earth to heaven, a transcendent experience."
In a statement to NBC News, they added: "He lived with fearless courage and a passion for experiencing all of life's adventures ... He passed as he lived, in an extraordinary way, watching the sunset, surrounded by people he loved, in his favorite place in the world."