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

itoggle caption Manuel Balce Ceneta/AP

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

itoggle caption Americans for Responsible Solutions

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

itoggle caption Larry Downing /Reuters /Landov

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

itoggle caption Joe Raedle/Getty Images

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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This AR-15 style weapon was on display in March at the 7th annual Border Security Expo in Phoenix, Ariz. It's among the type of weapons that advocates of new gun laws want to see banned. Joshua Lott /Reuters /Landov hide caption

itoggle caption Joshua Lott /Reuters /Landov

A Bushmaster rifle, similar to the type used by Adam Lanza during the shooting at Sandy Hook Elementary School, and some ammunition magazines. The sale and possession of this type of weapon, and high-capacity magazines, will be severely restricted in Connecticut under new legislation. Michelle McLoughlin /Reuters /Landov hide caption

itoggle caption Michelle McLoughlin /Reuters /Landov