|The suspected shooter is now in custody and being interrogated, according to Arizona police [AFP]
US congresswoman Gabrielle Giffords of Arizona has been shot in the head at point-blank range outside a supermarket in the city of Tucson while holding a public event. She survived the attack, but is in critical condition.
The shooting has prompted US legislators to postpone their agenda in Congress next week, delaying a vote on the repeal of US President Barack Obama's healthcare reform law, of which Giffords was a strong supporter.
Pima county Sheriff Clarence Dupnik has said that at least six people were killed in the attack, including Arizona's chief federal judge, a congressional aide to Giffords and a nine-year-old girl. He said that Giffords was the target of a gunman he described as mentally unstable, and possibly acting with an accomplice.
Dupnik said that at least 12 people, in addition to the congresswoman, had been wounded in the shooting.
Bob Walkup, the mayor of Tucson, told Al Jazeera that a suspicious package had also arrived at Giffords' office, and that a bomb disposal squad was called to examine it. That package was later found not to contain any explosive materials.
He said police are currently searching for an older man who was seen speaking with the suspected shooter, who has a criminal record, earlier in the day. Dupnik said that the suspect had been known to make death threats in the past, though he had never done so against Giffords.
Earlier, US news agencies reported that Giffords had died, but trauma surgeon Peter Rhee confirmed that she had undergone surgery and was in a critical condition.
"Gabrielle Giffords' condition is very optimistic," said Rhee. "It's about as optimistic as I can get in this situation."
Doctors said a bullet passed through Giffords' brain. Local television networks said late Saturday she was awake in her hospital bed and recognised her husband.
Dupnik said the attack ended only when two people tackled the gunman.
The dead include Arizona chief federal judge John Roll, Giffords' director of community outreach Gabe Zimmerman and a 9-year-old girl, Christina Greene.
Also killed were 76-year-old Dorthy Murray, 76-year-old Dorwin Stoddard, and 79-year-old Phyllis Scheck, investigators said.
President Obama, speaking at a press conference in Washington shortly after the shooting, called the incident an "unspeakable tragedy", saying that some victims had died while Giffords was "gravely wounded".
Janet Napolitano, homeland security secretary, issued a statement on the shooting, saying: "I am deeply saddened by reports that Congresswoman Gabrielle Giffords, Chief Judge John Roll and others were attacked ... There is no place in our society or discourse for such senseless and unconscionable acts of violence."
Al Jazeera's Nick Spicer, reporting from Washington DC, said that according to eyewitnesses, "bodies were lying on the sidewalk" outside the Safeway supermarket.
Giffords, he said, had been the target of threats and her office had earlier been vandalised after the US Congress voted on Obama's healthcare reform law in March.
National Public Radio reported that the suspected attacker, described as a male in his 20s, was "tackled by a bystander and taken into custody".
Mark Kimball, a communications staffer for Giffords, described the scene as "just complete chaos. People screaming, crying". According to his account, the gunman fired at Giffords and her district director, and then opened fire indiscriminately at staffers and others standing in line to speak with the congresswoman.
Over a hundred people held a candlelight vigil for the congresswoman, who was still in hospital, at her headquarters on Saturday night.
Spicer said that Giffords, a Democrat, was seen by Republicans as one to beat in the recent US midterm elections and was heavily criticised by 2008 vice-presidential candidate Sarah Palin.
"She was not somebody who was appreciated by the right wing of the Republican party," Spicer said.
"She had been singled out as someone who should be beaten at the polls, certainly, and she was somebody who supported healthcare reform which is really the landmark policy of Barack Obama's first term."
On the morning she was shot, Giffords was hosting a "Congress on the Corner" event - something she advertised on to her constituents as an opportunity to meet her and to discuss their concerns.
Chris Patyk, programme director of Tucson's KNST radio station, told Al Jazeera that Giffords is known for being "very personable" and that "it is easy to gain access and speak to Representative Giffords at an event like this, and that is why this news is all the more harrowing".
Giffords focused on immigration reform, military issues, stem cell research and alternative energy, as well as being a supporters of gun rights, while serving in Congress. She was married to US astronaut Mark Kelly.
'Vitriolic political rhetoric'
Sheriff Dupnik pointed to the vitriolic political rhetoric that has consumed the country as he denounced the shooting.
"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.
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 Washington, where Congress called of a key vote over healthcare reform next week, as politicians of all stripes denounced the shooting as a horrific and senseless act of violence. Obama dispatched FBI director Robert Mueller 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.
Law enforcement officials said members of Congress reported 42 cases of threats or violence in the first three months of 2010, nearly three times the 15 cases reported during the same period a year earlier. Nearly all dealt with the health care bill, and Giffords was among the targets.
Police say the shooter was in custody, and was identified by people familiar with the investigation as Jared Lee Loughner, 22. Pima County Sheriff's officials said he used a 9mm pistol to carry out the attack.
The suspect's exact motivation was not clear, but a former classmate described Loughner as a marijuana-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.