Millard Fuller, the visionary Christian with a single-minded, some say stubborn, focus that resulted in more than 300,000 houses built for the poor, died unexpectedly Monday night, The Atlanta Journal-Constitution reported.

Fuller, 74, was the driving force in founding Habitat for Humanity in 1976, a nonprofit that started in little Americus, Ga., but whose name is known around the world. After a rancorous split from the organization in 2005, he founded a new organization, the Fuller Center for Housing in Americus, which was doing the same work.

Millard Fuller founded Habitat for Humanity. He had been sick in recent days with chest congestion, said Holly Chapman, a spokeswoman for the Fuller Center, based in Americus.

Jackie Goodman of Atlanta, who volunteered with Habitat and the Fuller Center, said Fuller was well enough to participate Monday in a conference call with affiliates of the Fuller Center.

He got worse Monday night. His wife Linda told the Associated Press he was complaining of chest pains, headache and difficulty swallowing. He died in an ambulance that was taking him to a hospital Albany, Chapman said.

“We are all deeply saddened and in a state of shock,” she said.

Despite the recent illness, Fuller was vigorous and kept a busy schedule and had recently visited El Salvador.

Chapman said, “He was quite irritated that he had been sick lately, because he had never been sick a day in his life.”

Habitat for Humanity and the Fuller Center build houses for the poor in the U.S. and around the world. The families who live in the houses must help build them alongside volunteers, and they must pay back a no-interest loan that makes the housing affordable. Habitat attracts volunteers from across America, from blue collar workers to former presidents such as Jimmy Carter and Bill Clinton, from back-porch pickers to recording stars, all joining to nail shingles or drywall.

“Millard Fuller was one of the most extraordinary people I have ever known,” Carter said in a statement. “He used his remarkable gifts as an entrepreneur for the benefit of millions of needy people around the world by providing them with decent housing.”

Kent Watkins, who helps head up missions programs at Saint James United Methodist Church in Atlanta, said Fuller’s work not only changes the lives of those who live in Habitat and Fuller houses, but also the lives of volunteers.

“People go down on a project thinking they are going down to help somebody,” he said. “They come back changed by the experience.”

They become more giving, and volunteers rarely stop at helping build one house, he said.

Fuller started his new organization after splitting with Habitat, whose board fired him in 2005 for making “divisive” and “disruptive” comments.

He was not pleased with Habitat’s move to downtown Atlanta and the more bureaucratic approach of the new leadership, said Morris Dees, a college buddy and former law and business partner with Fuller in their early years. Dees founded the Southern Poverty Law Center, a civil rights organization. The two had become wealthy together before Fuller gave it up for what Dees called “his religious work.”

The Habitat board also investigated Fuller for sexual harassment but found “insufficient proof of inappropriate conduct.”

Goodman said Fuller put that chapter behind him and moved on, founding the Fuller Center to do homebuilding according to his own vision. “I think the more than 1 million people who live in homes built under Millard will say he was a giant of a man who changed their lives.”

Jonathan Reckford, the chief executive officer of Habitat for Humanity International, said in a press release, “Millard Fuller was a force of nature who turned a simple idea into an international organization that has helped more than 300,000 families move from deplorable housing into simple, decent homes they helped build and can afford to buy and live in. The entire Habitat family mourns the loss of our founder, a true giant in the affordable housing movement.”