In Operation Fast and Furious, federal agents from the US Bureau of Alcohol, Tobacco, Firearms and Explosives in Arizona abandoned the usual practice of intercepting all weapons they believed illicitly purchased. Instead, the goal of gun-walking was to track such weapons to high-level arms traffickers, and to dismantle their networks.

The agents in Arizona lost track of many of the weapons in the operation. Two of the guns that "walked" in the operation were found at the scene of the slaying of U.S. border agent Brian Terry.

A House committee has been investigating the operation and the Department of Justice's response to the investigation for more than a year. - AP