Billionaire David Koch has died at age 79. Koch was a major donor to conservative causes and educational groups.

A person close to the Koch family told The Associated Press on Friday that Koch had died. The person wasn't authorized to discuss the death and spoke on the condition of anonymity.

Together with his older brother, Charles, the Kochs were best known for a vast political network they built that became popularly known as the "Kochtopus" for its far-reaching tentacles in support of conservative causes.

The brothers founded the anti-tax, small government group Americans for Prosperity.

Koch was an engineer trained at MIT. He joined Koch Industries in 1970 and serves on its board. He was chief executive officer of Koch Chemical Technology Group, a Koch subsidiary.

Charles Koch released the following statement:

"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. Twenty-seven years ago, David was diagnosed with advanced prostate cancer and given a grim prognosis of a few years to live. David liked to say that a combination of brilliant doctors, state-of-the-art medications and his own stubbornness kept the cancer at bay. We can all be grateful that it did, because he was able to touch so many more lives as a result. "In those bountiful years, he married the lovely Julia Flesher, had three exceptional children, while remaining dedicated to the long-term success of Koch Industries. David also made institution changing philanthropic commitments to hospitals, cancer research, education and the arts. The significance of David's generosity is best captured in the words of Adam Smith, who wrote, 'to indulge our benevolent affections, constitutes the perfection of human nature.' "While this is a very sad day for us all, I want you to know that David was proud of the extraordinary work you all have done to make Koch Industries the successful company that it is today. He will be greatly missed, but never forgotten."

David retired as executive vice president of Koch Industries in 2018. He leaves behind his wife, Julia Koch, and three children. His family released this statement on his passing:

"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. "Yet, we wish for all to celebrate the life and impact of this most generous and kind man. He believed he had a responsibility to a world that had given him so many opportunities to succeed. David's philanthropic dedication to education, the arts and cancer research will have a lasting impact on innumerable lives - and that we will cherish forever."