NEW YORK (AP) ― J.C. Penney’s largest investor and former board member, William Ackman of Pershing Square Capital Management, is selling his nearly 18 percent stake in the company.

The move to sell 39.1 million shares of the company, announced in a regulatory filing late Monday afternoon, comes two weeks after Ackman resigned from J.C. Penney’s board as part of a deal to resolve an unusually public battle between the activist investor and the struggling department store operator.

The news sent its shares down nearly 3 percent to $13 per share in after hours-trading after closing down 15 cents to $13.35 in the regular session.

The latest development comes as the beleaguered chain is trying to recover from a botched transformation plan spearheaded by its former CEO Ron Johnson that led to disastrous financial results. The board ousted Johnson in April after only 17 months on the job and rehired Mike Ullman who had been CEO of the retailer from 2004 to 20011.

Ackman resigned from the board on Aug. 13, after he went public with statements saying he’d lost confidence in Penney’s board and that Chairman Thomas Engibous should be replaced. Ackman and the retailer’s board also were bickering over how quickly the company should replace Ullman who is expected to be an interim CEO.

Ackman joined Penney’s board in February 2011 and pushed the board to hire Johnson, a mastermind of Apple Inc.’s successful stores. The hope was Johnson could inject new energy into a tired company. But Penney ended up recording nearly a $1 billion in losses and a 25 percent drop in revenue in the first year of the transformation. Losses and declining revenue have continued into the first and second quarters of the year as Johnson’s legacy continues to cast a shadow over the company.

In a letter to investors last week, Ackman admitted that the investment in Penney was a “failure” and that retail “has not been our strong suit.”