What happened to Minnesota native missing in Yellowstone? His dad is determined to find out.

Austin King's fingers were frozen and he couldn't see clearly in the fog as he stood alone atop 11,000-foot Eagle Peak in Yellowstone National Park. Ruthless wind and sleet had hammered him en route, he scrawled shakily in the mountain summit's register on the evening of Sept. 17. He had "free soloed too many cliffs to get here," he wrote.

But he was exuberant that he'd made it, too.

"I am 22 years old and will never forget today the rest of my life. Life is beautiful. Go out and LIVE IT! -Austin King"

The young Winona native also attempted to call his parents and friends. His father missed his call and didn't receive the voicemail for another week, but Brian King-Henke learned later that his son had connected with his mother and wasn't well.

"You could hear in his voice … everything was going sideways," King-Henke told the Star Tribune.

It was the last anyone heard from Austin. His father made a copy of his son's register writing — a sort-of timestamp of King's dramatic day and, now, his disappearance.

What happened to the young man remains a mystery that his family is determined to solve, even while officials at the national park and in the region have scaled back their search.

King, a park concession worker since summer, had set off on a multiday backpacking trip to the highest point in Yellowstone in a challenging, mountainous part of the park's southeast section. When King didn't arrive for a scheduled boat pickup Sept. 20 at Yellowstone Lake, his absence triggered a massive search. Crews found some of his personal belongings at a campsite a half-day's hike from the base of the peak, but there was no other sign.

After an 11-day air-and-ground rescue mission covering thousands of miles and involving at least 100 searchers, the National Park Service (NPS) announced Oct. 2 that the effort to find King had transitioned to a recovery phase and would be limited.

His father is determined to learn his son's fate regardless. He started an online fundraiser and is in Cody, Wyo., about 40 miles east of Eagle Peak, coordinating his own search effort. He has no plans to return to Minnesota in the near term, he said. As many as 11 people were part of the search in the last 10 days, some with a history of volunteering in such cases. Some drove in from Montana and beyond.

Heavy snow thwarted searchers late Wednesday, and King-Henke is hoping that milder weather in the coming week might help the odds of getting back near Eagle Peak. The team had set up a basecamp at Eagle Creek trailhead in the Shoshone National Forest.

"We might have one more chance to get guys out there," he said.

NPS search-and-rescue crews dealt with 6-foot snow drifts during their search in late September. It's believed as much as a foot of snow fell Wednesday on Eagle Peak and the surrounding ridges.

King-Henke had hoped to use a helicopter service Tuesday to drop four ground searchers near Table Mountain, southwest of Eagle Peak, where they thought his son might have descended. NPS officials prohibited the helicopter's flight Monday night, King-Henke and others said.

In an e-mail Wednesday to the Star Tribune, park spokesperson Morgan Warthin said the NPS was cautioning the people helping King-Henke about the terrain and inclement weather to come.

"We continue to support this effort as much as possible while also considering the risks to lives and have provided the father information on the park's search efforts to date," Warthin added.

Two Montanans have been instrumental in helping form plans and spreading the word to others with search-and-rescue expertise, King-Henke said.

Roger Roots drove down from Livingston, Mont., to help. He backpacked in solo and climbed Eagle Peak between Oct. 11-13, but found no sign of King.

"It is an extremely difficult mountain to climb. There are rings of cliffs around it," Roots said.

John Lamb, a small business owner from Norris, Mont., north of West Yellowstone, decided to help, too, and enlisted others to assist in the search. He was there for a week until Wednesday, when the storm moved in.

King has been missing for nearly a month, and Lamb said elements of his story make it unlikely he survived. Search-and-rescuers found King's food bag at his campsite, in addition to his tent and sleeping pad, Lamb added. And, while King submitted his trip plan to a park staffer, saying that he intended to sleep overnight on the summit to watch the sunrise, he was inexperienced.

Lamb said it's possible King succumbed to cold weather or fell into a crevasse or ravine. That might explain why no one has found any trace of him, not even a missing backpack and sleeping bag from his campsite.

"Unless there is a miracle or something else, I don't see any indication where Austin was just hurt and holed up somewhere where there was food and shelter. There was no chance of that," he added. "Nothing has been found at all. That is the strange part about this. We usually find something."

King-Henke said he has been humbled by the help from searchers such as Lamb and Roots, and those supporting the effort in ancillary ways. Someone provided a camper for the Eagle Creek basecamp, and strangers arrived with hot food and firewood. Some offered the use of all-terrain vehicles.

Now, in limbo, King's father was frustrated Thursday that his own attempts at a search have met roadblocks from park service managers but is appreciative of anyone who has been involved from the beginning.

"The people that have been searching for him … I am honored for everything they have done. They have done the impossible as many hours they have put in," he said.

Lamb is prepared to assist again. Roots is back in Montana, but he's willing to return, too. He also praised King-Henke's perseverance.

"I think Brian is doing everything he can," Roots said. "He is going above and beyond what anyone else would do."

King-Henke said Lamb and others who've helped have talked about how to ramp up the search, even if it extends deep into 2025 when conditions are better.

"We're going to have our army," King-Henke said. "We're going to find him."