Czech billionaire Petr Kellner, owner of media group Central European Media Enterprises (CME), died in a helicopter crash in Alaska on Saturday.

Kellner’s company, PPF Group, acquired CME in Oct. 2020 from AT&T.

CME operates media businesses in five Central and Eastern European markets including Bulgaria, the Czech Republic, Romania, Slovakia and Slovenia. These operations comprise 30 television channels broadcasting to approximately 45 million people across the markets, including bTV in Bulgaria, Nova TV in the Czech Republic, Pro TV in Romania, TV Markiza in Slovakia and Pop TV in Slovenia.

Kellner had a net worth of $15.7 billion.

“With great sadness, PPF announces that on March 27, 2021, majority shareholder of PPF Mr. Petr Kellner tragically passed away in a helicopter accident in the Alaskan mountains. The incident, in which five lives were lost, is under investigation,” PPF said in a statement.

“Petr Kellner was 56 years old. His professional life was known for his incredible work ethic and creativity, but his private life belonged to his family. His funeral will be held with only close family members. We please ask the media to respect the privacy of the Kellner family during this difficult time.

“We want to express our gratitude for the condolences, well wishes, and prayers expressed so far to the bereaved.”

Four other people, including the pilot, died in the crash near Knik Glacier, and another is in a serious but stable condition, according to a statement by Alaska State Troopers.

CME was founded in 1994 with the launch of TV Nova in the Czech Republic. CME’s television brands are market and audience share leaders in all of its markets with a combined 2019 television advertising spend of approximately $916 million.

The PPF Group invests in financial services, telecommunications, biotechnology, real estate and mechanical engineering. The group owns assets worth €49 billion ($57.7 billion).