Stocks ended sharply lower Monday after crude oil closed at its lowest level since February 2009. Crude closed below $40 a barrel and some analysts warn the commodity could bottom out at $20 next year. Activist investor Carl Icahn and his Icahn Enterprises have offered to buy Pep Boys (PBY) for $15.50 a share. The offer puts a hitch in Bridgestone's previously accepted deal of $15 a share. Office Depot (ODP) tumbled after the FTC filed a complaint against Staples (SPLS) over its proposed takeover. Regulators said the $6.3 billion acquisition would create the largest office supplies retailer with little competition. Gun stocks pushed higher after a speech from President Obama on Sunday evening called for tighter regulation of firearms. Smith & Wesson (SWHC) and Sturm, Ruger & Co. (RGR) jumped.