TUCSON, Arizona - (AP) - Democratic Rep. Gabrielle Giffords ofArizona was shot in the head Saturday by a gunman who opened fireoutside a grocery store during a meeting with voters, killing afederal judge and five others in a rampage that rattled the countryand left Americans questioning whether divisive politics had pushedthe suspect over the edge.

Pima County Sheriff Clarence Dupnik said Giffords was the targetof a gunman whom he described as mentally unstable and possiblyacting along with an accomplice. He said Giffords was among 13people wounded in the melee that killed six people, includingArizona's chief federal judge, a 9-year-old girl and an aide forthe Democratic lawmaker. He said the rampage ended only after twopeople tackled the gunman.

The sheriff pointed to the vitriolic political rhetoric that hasconsumed the country as he denounced the shooting that claimedseveral of his friends as victims, including U.S. District JudgeJohn Roll. The judge celebrated Mass on Saturday morning like hedoes every day before stopping by to say hello to his good friendGiffords.

"When you look at unbalanced people, how they respond to thevitriol that comes out of certain mouths about tearing down thegovernment. The anger, the hatred, the bigotry that goes on in thiscountry is getting to be outrageous," the sheriff said. "Andunfortunately, Arizona I think has become the capital. We havebecome the mecca for prejudice and bigotry."

The reaction to the shooting rippled across the country asAmericans were aghast at the sight of such a violent attack on asitting member of Congress. The shooting cast a pall overWashington as politicians of all stripes denounced the shooting asa horrific and senseless act of violence. Capitol police askedmembers of Congress to be more vigilant about security in the wakeof the shooting, and some politicians expressed hope that thekilling spree serves as a wakeup call at a time when the politicalclimate has become so emotionally charged.

"It is a tragedy for Arizona, and a tragedy for our entirecountry," President Barack Obama declared.

Giffords, 40, is a three-term moderate Democrat who narrowly wonre-election in November against a tea party candidate asconservatives across the country sought to throw her from officeover her support of the health care law. Her office in Tucson wasvandalized in the hours after the House passed the overhaul lastMarch as anger over the law spread across the country.

Police say the shooter was in custody, and was identified bypeople familiar with the investigation as Jared Laugher, 22. PimaCounty Sheriff's officials said he used a 9 mm pistol to carry outthe attack. U.S. officials who provided his name to the AP spoke oncondition of anonymity because they were not authorized to releaseit publicly.