(CNN) -- A gunman intended to assassinate a U.S. representative when he opened fire outside a Tucson, Arizona, supermarket Saturday, killing six and wounding 12 including the congresswoman, the local sheriff said hours after the shooting. U.S. Rep. Gabrielle Giffords was in critical condition late Saturday after surgery for a single gunshot wound to the head. The dead included a federal judge and a 9-year-old girl, authorities said. One suspect was in custody immediately after the shooting, and investigators were "actively in pursuit" of a second man whom they believed may be involved in the attempted assassination, Pima County Sheriff Clarence Dupnik said Saturday night.
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NEW: Investigators are "actively pursuing" a second suspect in shooting
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A congressional aide, a federal judge and four other died in a shooting outside supermarket
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U.S. Rep. Gabrielle Giffords was wounded along with 11 others
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A suspect is in custody; law enforcement sources identify him as Jared Lee Loughner
@placeholder, 40, was shot once in the head at close range, authorities said.