Former President George W. Bush and his successor, President Obama, at the April 25 dedication of Bush's library on the campus of Southern Methodist University in Dallas. Larry W. Smith /EPA /LANDOV hide caption

itoggle caption Larry W. Smith /EPA /LANDOV

A Sig Sauer handgun on sale at a shop in Tucker, Ga. Erik S. Lesser /EPA /LANDOV hide caption

itoggle caption Erik S. Lesser /EPA /LANDOV

A gun shop in Glendale, Calif. Gabriel Bouys /AFP/Getty Images hide caption

itoggle caption Gabriel Bouys /AFP/Getty Images