The 91st richest man in the U.S., a roofing company billionaire, has died after falling through his home garage's roof, local authorities said Friday.

Ken Hendricks, 66, was checking on construction on the roof over his garage at his home in the town of Rock Thursday night when he fell through, Rock County Sheriff's Department commander Troy Knudson said. He suffered massive head injuries, according to his company, ABC Supply Co.

Hendricks' wife called authorities and attempted CPR on her husband, he said. Hendricks was taken first to a Beloit hospital and then transferred to Rockford Memorial Hospital in Winnebago County, Ill.

He was pronounced dead there early Friday morning, Winnebago County coroner Sue Fiduccia said. An autopsy is planned for Friday.

Hendricks was the founder, chairman and chief executive officer of the company, the self-described nation's largest wholesale distributor of roofing. The Beloit-based company does about $3 billion in business a year.

Hendricks had a net worth of $3.5 billion in September, according to Forbes magazine. That made him the country's 91st richest person, according to the magazine's ranking of American billionaires.

But he seemed unfazed by his wealth.

"It doesn't make any difference to me: I can't spend it," Hendricks said in an interview with Inc.com in September 2006. "I'd have to sell the company, and I'll sell the company over my dead body."

Hendricks, the son of a Janesville roofer, worked side-by-side with his father growing up. A high school dropout, he started his own roofing business at age 21, according to his biography on ABC Supply's Web site.

Tired of having to deal with multiple suppliers scattered around the country, he and his wife, Diane, started a national supply distribution chain in 1982.

The company celebrated its 25th anniversary this year, with 6,000 employees in 390 locations nationwide.

"This is an enormous tragedy and a great loss to the family, associates and the community," ABC Supply said in a statement.

Hendricks and his wife also owned a variety of companies through the Hendricks Holding Co. and a property development group with more than 25 million square feet of industrial and commercial real estate.

The couple had seven children, according to their biographies.