Shares of Dollar General plummeted on Friday making it TheStreet's Move of the Day. The discount retailer announced that CEO Rick Dreiling intends to step down from his post by next May or whenever the board of directors appoints a new chief. The decision comes as billionaire hedge fund investor Carl Icahn pressures the company to sell itself amid a tumbling share price. Dreiling said in the statement: "I am extremely proud of Dollar General's track record of success over the past six years, and I am honored to have had the opportunity to lead such an experienced and talented team. ... After considerable reflection, I am at a point where it is appropriate to begin to plan for my retirement. I plan to work with the Board of Directors on recruiting and mentoring a new CEO."