The billionaire industrialist and conservative donor David Koch has died, New Yorker reporter Jane Mayer said Friday, citing family sources. Koch Industries later confirmed the death.

David Koch and his brother Charles Koch have donated billions to an extensive network of conservative sources.

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The billionaire conservative donor and industrialist David Koch has died, his brother Charles said in a statement early Friday. Koch Industries confirmed the death shortly after.

"It is with a heavy heart that I announce the passing of my brother David. Anyone who worked with David surely experienced his giant personality and passion for life," Charles Koch wrote in the statement, adding that his brother had been diagnosed with prostate cancer 27 years ago.

"David liked to say that a combination of brilliant doctors, state-of-the-art medications and his own stubbornness kept the cancer at bay," Charles Koch wrote. "We can all be grateful that it did, because he was able to touch so many more lives as a result."

"While we mourn the loss of our hero, we remember his iconic laughter, insatiable curiosity, and gentle heart. His stories of childhood adventures enlivened our family dinners; his endless knowledge rendered him our 'walking Google.' His sensitive heart had him shed a tear at the beauty of his daughter's ballet, and beam with pride when his son beat him at chess. We will miss the fifth link in our family."

The death was first reported by New Yorker reporter Jane Mayer, who tweeted Friday morning that she had been told by family sources that Koch had died. Her 2016 book, "Dark Money," focused on the influence of the Kochs on American politics.

Koch, 79, and his brother Charles, 83, have been among the most influential figures in the conservative movement in the US in recent years, having donated hundreds of millions to a network of conservative organizations.

Koch shared majority control of the privately held industrial conglomerate Koch Industries with his brother Charles, according to Forbes. Koch's wealth, estimated at $53.5 billion, meant that the two brothers were tied as the seventh-richest Americans according to the Forbes 400 ranking.

Charles and David Koch. YouTube/AP

Koch began working in the family-owned business in 1970 and held the title of executive vice president until his retirement in June 2018.

Koch Industries has had a controversial environmental record. According to a 2014 Rolling Stone article, the company paid millions in regulatory fines and legal settlements throughout the 1990s and early 2000s related to various environmental violations. Koch Industries and the Koch brothers have continued to be a target of environmental groups such as Greenpeace.

David Koch in 2017. Lars Niki/Getty Images for United States Olympic Committee

But Koch was best known for his staunch support of conservative and libertarian causes. He ran as the vice presidential candidate for the Libertarian Party in the 1980 presidential election. In the decades after, the Koch brothers became some of the largest donors to conservative causes in the US, reportedly raising hundreds of millions of dollars for Republican candidates in recent elections.

The Koch brothers' main political-advocacy group, the Americans for Prosperity Foundation, which David headed until his June 2018 retirement, was one of the main backers of the Tea Party movement, which began in opposition to President Barack Obama's policies. But David Koch distanced himself from membership in the Tea Party itself.

David Koch accepts the Laureate Award at the Lincoln Center Spring Gala at Alice Tully Hall on May 2, 2017, in New York. Getty Images

Koch was a figure in Manhattan's upper crust and a major donor to several charitable causes and cultural organizations. Koch gave millions of dollars to the American Museum of Natural History in New York and served on its board for 23 years before resigning in 2016. In 2008, Koch gave a $100 million donation to the Lincoln Center to renovate the New York State Theater, which was renamed after the billionaire.

After receiving a prostate-cancer diagnosis in 1992, Koch became a major supporter of cancer research, donating to Johns Hopkins, the Memorial Sloan Kettering Cancer Center, and his alma mater, MIT.

Koch is survived by his wife, Julia Flesher Koch, and his children David, Mary, and John.