President Obama speaks in April after the Senate rejected a bill that would expand background checks on guns. The White House is seeking to clarify rules that bar firearm possession due to mental health problems. Manuel Balce Ceneta/AP hide caption

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New York City Mayor Michael Bloomberg displays a confiscated AR-15 assault rifle in East Harlem as District Attorney Cy Vance (right) looks on during a news conference in October 2012 in New York City. Mario Tama/Getty Images hide caption

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Former Rep. Gabby Giffords and her husband, Mark Kelly, at a gun show in Saratoga Springs, N.Y., in October. Giffords was shot in the head in a 2011 mass shooting in Tucson. She and Kelly have since founded a political action committee to push for tougher gun laws. Tim Roske/AP hide caption

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Former Rep. Gabrielle Giffords, D-Ariz., at a firing range in Nevada earlier this week. Her husband, retired astronaut Mark Kelly, was behind her. Americans for Responsible Solutions hide caption

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None of the possibly ricin-tainted letters mailed to President Obama have reached the White House, authorities say. They were intercepted at a remote mail handling facility. Larry Downing /Reuters /Landov hide caption

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Detective Enrique Chavez logs weapons from a gun buyback in Miami. Arizona's new law requires municipalities to re-sell weapons recovered in such programs. Joe Raedle/Getty Images hide caption

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Francine Wheeler, seen here delivering the presidential address alongside her husband, David, urged the Senate to pass gun control legislation. YouTube hide caption

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