Billionaire conservative activist David Koch died at 79.

American billionaire industrialist David Koch, a major financier of political candidates who supported gay rights, same-sex marriage, and stem-cell research, has died at age 79, his brother has announced.

“It is with a heavy heart that I announce the passing of my brother David,” Charles Koch said in a statement on Friday. “Anyone who worked with David surely experienced his giant personality and passion for life.”

“He will be greatly missed, but never forgotten,” Koch said in the statement addressed to employees. “David was proud of the extraordinary work you all have done to make Koch Industries the successful company that it is today.”

The Koch brothers, two of the Republican Party’s biggest donors, wield significant financial and political influence on US politics, both directly and indirectly, via various advocacy and lobbying organizations. They also contributed to Democratic candidates.

David was a driving force behind conglomerate Koch Industries, the Wichita, Kansas-based energy and the chemical company he ran with Charles. The brothers were tied as 11th richest in the world in a ranking by Forbes. At the time of his death, David was worth $42.4 billion.

David stepped down from the business and political activities in June 2018, citing declining health.

American journalist and political analyst Don DeBar said, “David Koch is to Democrats what George Soros is to others. To Democrats, he is the Satan that drives the evil Republican agenda.”

“It’s evidence of their lack of a serious, systemic critique. It’s the Democratic version of Republicans and some others who blame Soros for the sins of the system that produced him,” he added.

“Are these people destructive and exploitative players who cause a lot of damage to millions of people around the world? Yes. But they are actors on a stage where there are ten understudy actors lying in wait to replace any actor in the ongoing play,” the analyst noted.

“The problem, and therefore the solution, is systemic. As we will see, yet again, when the death of this particular person changes nothing for the rest of us,” he concluded.