Atlanta business leader and philanthropist Charlie Loudermilk, the 85-year-old founder of multi-billion-dollar rent-to-own business Aaron's, is stepping down from the company he started nearly 60 years ago.

Loudermilk slowly had eased himself away from Aaron's, beginning in 2008 when he left as CEO of the company, but he had remained chairman of the board. He announced Monday he will leave that role in mid-September, becoming chairman emeritus.

Aaron's did not make Loudermilk available for comment and attempts to reach him were unsuccessful. But board members and executives said they were shocked to learn of his decision.

"We were as surprised as anyone," said Ray Robinson, Aaron's lead director and the chairman of Citizens Trust Bank. "We had no intention of him leaving."

The decision to leave was Loudermilk's alone, the board members and executives said.

Robinson and another member of Aaron's board, Leo Benatar, said they believe Loudermilk's announcement was precipitated by his son Robin's exit from the business.

After succeeding his father as CEO, Robin Loudermilk left the company last November, citing anxiety and depression. The board members said Charlie Loudermilk seemed to reassess his involvement in the company after his son stepped down. They expect him to become involved in Robin Loudermilk's real estate business in his retirement.

Robin Loudermilk was traveling and was unavailable for comment about his father's plans, though a spokeswoman for his company said in an email that Charlie Loudermilk has always been very active in the family's real estate investments and will continue to be active in both existing and new projects.

Charlie Loudermilk, who was born in Atlanta, started Aaron's in 1955 after borrowing $500. In the beginning, he kept the business alive by kiting checks, writing them from one account to another and hoping the funds were not deposited too soon. He built the Atlanta-based rent-to-own furniture company into a $2 billion business, with 1,985 stores nationwide.

Along the way, Loudermilk chaired the MARTA board and the successful mayoral campaign of former UN Ambassador Andrew Young, bringing the business community behind Young.

He has donated more than $35 million to various causes in metro Atlanta and elsewhere, worked to revitalize Buckhead, and led the development of the downtown meeting venue the Loudermilk Center.

Young said Loudermilk did not inform him of his decision, though the two remain close. He said the news was unexpected, even though Loudermilk has been orchestrating his departure for some time.

"It's something we're all trying to do, make better use of our brains rather than our energy," Young said. "He's entitled to do what he wants with whatever life he has left."

A year ago, Loudermilk said his age had forced him to slow down. His knees were giving out, he said, and though he enjoys working, he was not able to maintain the same pace he once did.

"You get to my age, there are some things you do to tell your grandchildren, great-grandchildren you've given back," he said in 2011.

In a statement, Loudermilk called leaving Aaron's "one of the most difficult decisions I have ever made," but said he decided the time had come to "focus on personal endeavors that bring me joy."

Ron Allen, Aaron's president and CEO, said that when he took that role Loudermilk told him he saw it as a transition period.

Though Loudermilk has still come to the office every day, he has been less active than he once was, said Gilbert Danielson, Aaron's executive vice president and chief financial officer.

There are no plans to change the company's business model, Danielson said. With 4.2 million shares of Aaron's stock, Loudermilk owns about 5.6 percent of the company. The board has not yet decided who will take over as chairman.

Loudermilk's influence and the long tenure of many Aaron's executives should mean his departure has little impact on the business, they said. In the past, analysts have commented on the depth and knowledge of Aaron's leadership.

"He certainly will be missed," Danielson said, "but he leaves a good team behind to carry on."

When Loudermilk met with the board this month to announce his decision, he polled the directors about the retirement ages at their own companies, said Benatar, the former CEO of packaging company Engraph. Hearing that they ranged from 65 to 75 reassured Loudermilk that he had made the right decision, Benatar said.

Benatar, also an Atlanta native, said Loudermilk's name is at the top of the list when he thinks of people who have had an impact on the city. Robinson said Loudermilk has always felt a responsibility to the city of Atlanta.

"Charlie's right at the heart of it," he said. "Every time you turn around, there's something Charlie has done."

Young said he expects Loudermilk to remain up-to-date with Aaron's and to remain active in Atlanta. Loudermilk owns the Buckhead Theatre and continues to donate money, including $1 million this year to the Atlanta Police Foundation.

If he's interested, Young said, there will still be plenty of people who seek Loudermilk's involvement and counsel.

"He's still very influential in every sector of the community," Young said. "I think Charlie Loudermilk is in a position to be a respected elder in this community for years to come."