OKLAHOMA CITY -- Walgreen's ( WAG) Chairman and CEO Jeffrey Rein has decided to step down two days after the company abandoned its plans to buy Longs Drug Stores ( LDG).

Rein joined Walgreen 26 years ago and helped build the company into the nation's largest drugstore chain. He lasted just two years as CEO and one as chairman of the board. At the age of 56, he is leaving nearly a decade before most people choose to retire at the company.

Walgreen gave no reason for Rein's sudden departure when announcing the news on Friday. Instead, newly appointed Chairman Alan McNally simply thanked Rein for his "outstanding contributions" and expressed "respect" for his decision to retire. McNally will double as interim CEO until a permanent leader can be found.

Two years ago, Rein looked like Walgreen's answer. In tapping him as CEO, Walgreen said the move was part of its official "long-range leadership succession" plan.

""He's had proven success building our people and our business in the Southwest, and he's done the same at the national level through 10 very productive years in several key corporate positions," Walgreen said of Rein at the time. "There isn't a segment of our business in which Jeff hasn't been intimately involved, and he's a key player in our strategy and our operations.

"He's providing strong, energizing leadership as president and will continue to do so as CEO."

Last year, Walgreen went a step further when it named Rein chairman of the board and called him the ideal leader for the company.

Since then, Walgreen has shifted away from the familiar strategy that brought the company so much success. Instead of simply building more and more of its own popular drugstores, the company started considering acquisitions as well.

Walgreen's latest takeover attempt backfired in dramatic fashion, though. The company tried to buy Longs, although Longs had already agreed to sell itself to CVS-Caremark ( CVS).

Although Walgreen offered to pay more, Longs continued to embrace its deal with CVS. After months of fighting, Walgreen finally abandoned its $3 billion bid for Longs when the market collapsed this week.

Less than 48 hours later, Rein has departed with the briefest of farewells.

"It has been a tremendous honor to serve Walgreens," Rein said in Friday's press release. "Walgreens is one of America's finest corporations, and I am proud of our accomplishments over the years in building America's largest drugstore chain offering consumer goods and services and serving the health and wellness needs of millions of Americans.

"I have great confidence in the company's future, and I thank our 226,000 employees for their exceptional dedication and commitment to Walgreens."

Walgreen's shareholders seemed quite shaken by the news, pushing the company's stock down 11% to a new 52-week low of $22.52.

More from Stocks

Stacey Cunningham: From Intern to Head of the New York Stock Exchange

Stacey Cunningham: From Intern to Head of the New York Stock Exchange

China Gives Tesla, Ford, General Motors and Trump One Awesome Present

China Gives Tesla, Ford, General Motors and Trump One Awesome Present

Oil Prices, China Tariffs, Micron and Kohl's - 5 Things You Must Know

Oil Prices, China Tariffs, Micron and Kohl's - 5 Things You Must Know

The Great American Supermarket No Longer Reigns Supreme

The Great American Supermarket No Longer Reigns Supreme

Kroger CEO: Even in the Age of Amazon, Physical Stores Will Still Be Important

Kroger CEO: Even in the Age of Amazon, Physical Stores Will Still Be Important