ANCHORAGE: A helicopter carrying guides and guests on a heli-skiing excursion north of Anchorage slammed into a mountain and then rolled downhill hundreds of feet, killing the pilot and four of the five passengers, officials said Monday.

Among the dead in the Saturday evening crash was billionaire Petr Kellner, the richest man in the Czech Republic. The survivor, identified as David Horvath, 48, of the Czech Republic, was listed in serious condition Monday, said Mike Canfield, a spokesman at Providence Alaska Medical Center in Anchorage.

The chartered helicopter, an Airbus AS350 B3, was “conducting heli-ski operations in an area of steep and remote terrain within the Chugach Mountains near Knik Glacier,” National Transportation Safety Board member Tom Chapman said Monday during a briefing with reporters.

The crash site, about 21 miles (34 kilometers) southeast of Palmer, is only accessibly by helicopter because of the rugged terrain and snowy conditions. Palmer is located about 45 miles (72 kilometers) north of Anchorage.

Recovery of the bodies was accelerated on Sunday because another snowstorm is forecast. The bodies were turned over to the Alaska State Medical Examiner.

Clint Johnson, the NTSB’s chief in the Alaska division, was also able to document the crash site with photos from the air “before the snowfall could obscure the site,” Chapman said.

Recovery of the wreckage is now the main focus for investigators, but that timing is uncertain given the terrain and forecast of additional snow.

The five people killed were identified as Kellner, 56, and Benjamin Larochaix, 50, both of the Czech Republic; Gregory Harms, 52, of Colorado; and two Alaska residents, Sean McManamy, 38, of Girdwood, and the pilot, Zachary Russel, 33, of Anchorage, troopers said Sunday. Authorities initially released McManamy’s name as McMannany.

The five passengers included three guests and two guides from the Tordrillo Mountain Lodge, said company spokesperson Mary Ann Pruitt.

Kellner was a businessman with a net worth over $17 billion, according to the Forbes 2020 list of the world’s richest people.

Kellner owned a 98.93% stake in the PPF Group, an international investment company. The group operates in 25 countries in Europe, Asia and North America with assets of $52 billion (44 billion euros). PPF Group confirmed Kellner’s death.

“His professional life was known for his incredible work ethic and creativity, but his private life belonged to his family,” a message posted on the PPF Group website said.

The funeral is planned for only close family members, and the company asked the media to respect the privacy of the family.

Kellner and Larochaix “were loyal and frequent” guests at the lodge, Pruitt said in an email to The Associated Press. Vacation packages at the lodge start at $15,000 per person.

Harms was a pioneering heli-ski guide in Alaska and worked for many years at the lodge, Pruitt said.

“Greg was one of the most experienced guides in the business,” she said. He also founded a heli-ski company that led trips across the world.

McManamy had been a guide for over 10 years and had been with the lodge for the last five, she said. He was also an experienced mountain guide on Denali, North America’s tallest peak.

Russel was a pilot for Soloy Helicopters, a company based in the small city of Wasilla that is contracted by the lodge to provide transportation, Pruitt said.

“This news is devastating to our staff, the community in which we operate and the families of the deceased,” a statement from the lodge said.

Chapman, the NTSB member, said based on Johnson’s observations, the helicopter appears to have hit the mountain 10 feet (3.05 meters) to 15 feet (4.57 meters) below a ridgeline at an elevation of approximately 5,500 feet (1,676 meters). The helicopter then rolled 800-900 feet (244-274 meters) downhill.

Using satellite-based signals broadcast from the helicopter, the NTSB said the aircraft was last heard from at 6:34 p.m. Saturday and reported overdue at about 8:30 p.m. Another operator participating in the search found and identified the wreckage about an hour later, Chapman said.

Chapman said the team investigating the crash will look at airworthiness, operations, meteorology, structures, helicopter performance, recording devices and human performance.

“Our mission is to understand not just what happened, but why and to recommend changes to prevent it from happening again,” he said.

The NTSB does not yet have precise information about the weather at the time of the accident, but preliminary reports have indicated it was relatively clear, he said.

Chapman said it was his understanding the helicopter carried some type of recording equipment on board, but he couldn’t immediately say if it was a black box. If it did have some type of recording device, “that will be an important part of the investigatory process,” he said.

The NTSB is also hoping to interview the survivor, but investigators have not yet had direct contact with Horvath. It’s also not yet known if there was any type of communication from the pilot before the crash.