Robert Murray was diagnosed with black lung disease in 2016
Robert Murray
Robert Murray
| Credit: Spencer Weiner/Los Angeles Times via Getty

Robert Murray, a high-profile coal executive, has died. He was 80.

Murray, who was known as the "King of Coal," died from lung disease complications on Sunday in Ohio, CNN reported Monday.

Murray long advocated against environmental protections and federal regulations that would reduce black lung disease, which he was diagnosed with in 2016.

According to the Pittsburgh Post-Gazette, Murray was known to bring oxygen along with him to coal industry events after his diagnosis.

Earlier this month, Murray filed an application for black lung benefits with the U.S. Department of Labor, the Associated Press reported. In the application, Murray reportedly said that he was "near death" and dependent on oxygen.

Murray was previously the president and CEO of Murray Energy Holdings, which went through bankruptcy and emerged as American Consolidated Natural Resources Holdings. Murray retired from his position as chairman of the board of directors just last week.

Robert Murray
Robert Murray
| Credit: Justin Sullivan/Getty

The son of a coal miner, Murray first began his career in coal as a 17-year-old and eventually worked his way up to become the CEO of North American Coal Corporation. He was fired from the job in 1987 in a dispute over pensions.

After that, he founded the company that would become Murray Energy. The company had a record of disregarding safety rules, according to the New York Times.

A Donald Trump supporter, Murray also donated thousands to organizations that were focused on rolling back environmental protections.

"Bob fought through his medical challenges with the same energy, drive, guts, and faith as he approached everything in life," Ohio Governor Mike DeWine said in a statement on Twitter Monday. "In any conversation we had, Bob talked about his faith in God, his love of family, and his dedication to his employees. Fran & I will deeply miss him."

Murray's lawyer Michael Shaheen tells PEOPLE that his death "marks the end of a lifetime of  work that affected not only coalminers and their families in the Ohio Valley but across the country."

Calling Murray an "icon," Shaheen describes him as "diligent, determined, driven and extremely intelligent," and "extremely philanthropic."

"I represented him on various matters over the last 20 plus years," Shaheen says. "We became very close over the last year or so. He was always very kind to me. He’d give me advice on life, family and business. I cherish the time I had with him."

The American Consolidated Natural Resources did not immediately respond to PEOPLE's request for comment Tuesday.