Pima County Sheriff Clarence Dupnik said Giffords was the target of a gunman whom he described as mentally unstable and possibly acting along with an accomplice. He said Giffords was among 13 people wounded in the melee that killed six people, including Arizona's chief federal judge, a 9-year-old girl and an aide for the Democratic lawmaker. He said the rampage ended only after two people tackled the gunman.
Doctors were optimistic about Giffords surviving as she was responding to commands from doctors despite having a bullet go through her head. "With guarded optimism, I hope she will survive, but this is a very devastating wound," said Dr. Richard Carmona, the former surgeon general who lives in Tucson.
The sheriff pointed to the vitriolic political rhetoric that has consumed the country as he denounced the shooting that claimed several of his friends as victims, including U.S. District Judge John Roll. The judge celebrated Mass on Saturday morning like he does every day before stopping by to say hello to his good friend Giffords.
"When you look at unbalanced people, how they respond to the vitriol that comes out of certain mouths about tearing down the government. The anger, the hatred, the bigotry that goes on in this country is getting to be outrageous," the sheriff said. "And unfortunately, Arizona I think has become the capital. We have become the mecca for prejudice and bigotry."
The reaction to the shooting rippled across the country as Americans were aghast at the sight of such a violent attack on a sitting member of Congress. The shooting cast a pall over the Capitol as politicians of all stripes denounced the shooting as a horrific and senseless act of violence. Obama dispatched his FBI director to Arizona. Capitol police asked members of Congress to be more vigilant about security in the wake of the shooting, and some politicians expressed hope that the killing spree serves as a wakeup call at a time when the political climate has become so emotionally charged.
"It is a tragedy for Arizona, and a tragedy for our entire country," President Barack Obama declared.
Giffords, 40, is a three-term moderate Democrat who narrowly won re-election in November against a tea party candidate as conservatives across the country sought to throw her from office over her support of the health care law. Her office in Tucson was vandalized in the hours after the House passed the overhaul last March as anger over the law spread across the country.
Police say the shooter was in custody, and was identified by people familiar with the investigation as Jared Loughner, 22. Officials said he used a semiautomatic 9-mm pistol with an extended clip to carry out the attack. U.S. officials who provided his name to the AP spoke on condition of anonymity because they were not authorized to release it publicly.
The suspect's exact motivation was not clear, but a former classmate described Loughner as a pot-smoking loner who had rambling beliefs about the world. The Army said he tried to enlist in December 2008 but was rejected for reasons the military did not provide.
Federal law enforcement officials were poring over versions of a MySpace page that belonged to Jared Loughner and over a YouTube video published weeks ago under an account "Classitup10" and linked to him. The MySpace page, which was removed within minutes of the gunman being identified by officials, included a mysterious "Goodbye friends" message published hours before the shooting and exhorted his friends to "Please don't be mad at me."
In one of several YouTube videos, which featured text against a dark background, Loughner described inventing a new U.S. currency and complained about the illiteracy rate among people living in Giffords' congressional district in Arizona.
"I know who's listening: Government Officials, and the People," Loughner wrote. "Nearly all the people, who don't know this accurate information of a new currency, aren't aware of mind control and brainwash methods. If I have my civil rights, then this message wouldn't have happen (sic)."
Giffords spokesman C.J. Karamargin said three Giffords staffers were shot. One died, and the other two are expected to survive. Gabe Zimmerman, a former social worker who served as Giffords' director of community outreach, died. Giffords had worked with the judge in the past to line up funding to build a new courthouse in Yuma, and Obama hailed him for his nearly 40 years of service as a judge.
An uncle of the 9-year-old girl told the Arizona Republic that a neighbor was going to the event and invited her along because she had just been elected to the student council and was interested in government.
Giffords was first elected to Congress amid a wave of Democratic victories in the 2006 election, and has been mentioned as a possible Senate candidate in 2012 and a gubernatorial prospect in 2014.
Giffords is married to astronaut Mark E. Kelly, who has piloted space shuttles Endeavour and Discovery. The two met in China in 2003 while they were serving on a committee there, and were married in January 2007. Sen. Bill Nelson, chairman of the Senate Commerce Space and Science Subcommittee, said her husband is training to be the commander of the space shuttle mission slated for April. His brother is currently serving aboard the International Space Station, Nelson said.
Giffords, known as "Gabby," tweeted shortly before the shooting, describing her "Congress on Your Corner" event: "My 1st Congress on Your Corner starts now. Please stop by to let me know what is on your mind or tweet me later."
"It's not surprising that today Gabby was doing what she always does, listening to the hopes and concerns of her neighbors," Obama said. "That is the essence of what our democracy is about."