Shares of Lehman have been hammered in recent weeks amid growing investor concern over the firm's balance sheet. On Monday, Lehman pre-announced a $2.8 billion loss and that it would raise $6 billion in new capital to bolster its balance sheet, which is bleeding losses because of soured loans on its books. On Thursday, CNBC was first to report that Erin Callen, the firm's chief financial officer, and Joe Gregory, Lehman's president, were stepping down from their posts, only adding to investor concerns about Lehman's future.