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Margin calls can be merciless, as the founder of Green Mountain Coffee Roasters has now found out.

The founder, Robert P. Stiller, lost his post as chairman of the board on Tuesday after he sold five million shares, worth around $125.5 million, to pay off loans he had taken out against his sizable stock holdings in the company.

Another director, William D. Davis, has been removed from his position as lead director of the board after he sold 548,000 shares of company stock as a result of a margin call.

The company — known for its Keurig single-cup coffee pods and brewers — called the forced sales “disappointing” and said that they “were inconsistent with the company’s internal trading policies.” Both men will also give up their board committees but will remain as directors. Michael J. Mardy has been named interim chairman.

Shares of Green Mountain nearly halved last week after delivering a disappointing earnings report on May 2. Mr. Stiller’s shares were sold on Monday, while Mr. Davis’s were sold on Friday and Monday. In after-hours trading on Tuesday, the shares fell more than 4 percent.

Until last fall, Green Mountain was the best-performing stock on major exchanges over a five-year period. Then, it became a target of short-sellers, in particular David Einhorn, who runs the hedge fund Greenlight Capital. Mr. Einhorn questioned the company’s accounting and capital expenditures among other issues.

Still, the long ascent had made fortunes for Green Mountain’s employees. And Mr. Stiller, who founded the company in 1981, became a billionaire. Last year, he acquired a $17.5 million apartment on New York’s Upper West Side that had belonged to Tom Brady, quarterback for the New England Patriots.

Founders of companies often keep a large share of their wealth in the business that made them rich. But what’s unusual about Mr. Stiller’s case is the size of the loans he took out against his stake in Green Mountain. As of Jan. 26, 12.6 million of his shares, or 78 percent of his total personal holdings, were pledged as collateral against loans, according to a securities filing. At the time, the pledged shares would have been worth around $619 million.

As the shares plunged, the banks have been able to force sales to ensure that their loans to Mr. Stiller stayed in line with the lower value of the shares. The selling weighed on the stock price, adding to the pain of other shareholders in the last week.

The high level of loans taken out by Mr. Stiller raises important questions about how executives handle large stakes. Taking out loans against shares allows an executive to raise cash from a stake without actually selling it. But if the shares plunge, the resulting margin call may lead to an especially brutal wave of selling. Mr. Stiller didn’t always have loans against most of his stake. In 2008, for instance, 46 percent of his shares were used to back loans.

In theory, when a margin call comes, an executive could use other liquid collateral to back the loans, instead of selling the shares against which the loans were made. And Mr. Stiller most likely has other assets that he acquired after selling out of large amounts of Green Mountain shares.

From August 2003 till April 2012, Mr. Stiller made a net gain of $216 million from selling Green Mountain shares, according to Equilar, an executive compensation data firm. His most lucrative sale appeared to take place in August last year, when he pocketed $54 million from selling a batch of shares at $107, close to Green Mountain’s highest share price ever. Mr. Stiller, who was chief executive of Green Mountain until May 2007, raised $66 million from selling a million shares in February.

Mr. Stiller has also built up a large stake, worth around $50 million, in Krispy Kreme Doughnuts. Shares in that company tumbled over 9 percent on Tuesday, on fears that Mr. Stiller may liquidate some of his Krispy Kreme to steady his finances.

Mr. Stiller’s personal stake has fallen as result of his selling. Since the margin-call sale, he now owns about 5.4 percent of Green Mountain. But if he were to sell shares that are backing loans still outstanding, his stake would drop to 1.86 million shares, which is about 1.2 percent of the company. In early 2008, Mr. Stiller owned 27.5 percent of Green Mountain.