Sources tell CBS News, the investigators will be speaking with gun shop owners the ATF allegedly recruited to play a part in Operation Fast and Furious. In that operation, insiders allege ATF allowed more than 2,500 assault rifles and other weapons to hit the streets or "walk." The idea was allegedly to monitor the purchases of gun buyers suspected of working with Mexican drug cartels, in hopes it would eventually provide intelligence to take down a cartel. But some of the weapons have been used in violent crimes, including the scene of the murder of border patrol agent Brian Terry last December.

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