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Full coverage: ATF's Fast and Furious scandal

ATF’s Fast and Furious scandalA federal operation dubbed Fast and Furious allowed weapons from the U.S. to pass into the hands of suspected gun smugglers so the arms could be traced to the higher echelons of Mexican drug cartels. The Bureau of Alcohol, Tobacco, Firearms and Explosives, which ran the operation, has lost track of hundreds of firearms, many of which have been linked to crimes, including the fatal shooting of Border Patrol Agent Brian Terry in December 2010.

A U.S. Border Patrol agent arrives for a memorial service for slain comrade Brian Terry on Jan. 21, 2011, in Tucson. Terry was killed during a shootout the month before near the U.S.-Mexico Border. (John Moore / Getty Images)