Ron Johnson, whose stormy tenure as CEO of J.C. Penney came to an end Monday, is seen here announcing a new strategy for the retail chain last year. AFP/Getty Images April 8, 2013, 2:45 p.m. Ron Johnson is no longer chief executive of J.C. Penney, and will be replaced by his predecessor, Myron E. Ullman III. Johnson had been trying to revamp the J.C. Penney brand by perking up the department store's product assortment while downsizing its staff head count. But rumors that he was on his way out began circulating months ago, after J.C. Penney's revenue tanked 25% in a single quarter, its stock plummeted about 60% in a year and customers complained loudly about the company's flip-flopping policies on discounts and bargains. His critics included William Ackman, manager of Pershing Square Capital Management, J.C. Penney's largest shareholder. On Friday, Ackman said Johnson had made "some very big mistakes" in his strategy. "The impact has been ... something very close to a disaster," Ackman said. Johnson joined J.C. Penney in late 2011 from Apple, where he spearheaded the technology giant's sleek stores and Genius Bar concept. His position at Apple remains open.