U.S. Representative Gabrielle Giffords of Arizona, above with House Speaker John Boehner, is in critical condition after being shot in the head in her district. ((Susan Walsh/Associated Press))

Another suspect is being sought in the deadly shooting outside a Tucson, Ariz., grocery store Saturday that killed six people and critically wounded a U.S. congresswoman, whom officials say was the target of the attack.

Pima County Sheriff Clarence Dupnik said authorities are not convinced the alleged gunman, who was tackled by "two brave individuals," acted alone in the shooting. U.S. Representative Gabrielle Giffords of Arizona, who was shot in the head, was among at least 19 people shot.

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Pima County Sheriff Clarence Dupnik briefs reporters on the shooting.

"There's some reason to believe he came to this location with another individual," Dupnik said at a news conference Saturday night, adding they have pictures of a second suspect.

Dupnik said the suspect in custody, who has been identified as 22-year-old Jared Loughner, had a criminal background, was a college student and that there had been "some difficulties with him."

Dupnik said the gun used in the shooting was a semi-automatic pistol.

"I think yes, [Giffords] was the target," Dupnik said.

Dr. Peter Rhee of the University Medical Center in Tucson said he was "very optimistic" about Giffords's recovery.


Emergency personnel work at the scene where Gabrielle Giffords and others were shot outside a Safeway grocery store in Tucson, Ariz. ((Matt York/Associated Press))


Eyewitness account

Dr. Steven Rayle told CBC News how he had gone with a friend to meet Giffords at the Safeway store and was walking toward her when the shooting began.

"I proceeded around sort of a concrete post to the side of the table, and as I looked up, I saw a man shoot Congressman Giffords in the head and then he immediately began rapid fire [at] everybody who was around in the area."

Rayle said it wasn't a large crowd, about 25 people.

"There were several people who appeared to be mortally wounded right away. There was a gentleman who was lying on his face, unresponsive. There were several other people. There were people who had been shot," he said.

Rayle said when the shots were fired, he initially thought it was some sort of stunt because the gunfire didn't sound real.

"But of course it was and then I ducked behind this concrete post out of the way of the shooter who was continuing to shoot," he said. "I sensed that he was coming around beyond the table to leave and he was still shooting and I got down on the ground and laid there as if I had been shot so that he didn't see me standing."

Rayle said that a doctor in such a situation would try to triage as best as possible, but that there's not a lot that can be done. He said at least five people were given CPR and that Giffords was propped up.

"I could see that she had been shot in the head. A staffer was attending to her. She was very bloody and I could see that she was conscious. She was moving her fingers and hands and had moved her arms so I was hopeful that those were not fatal wounds for her."

U.S. District Judge John Roll and a nine-year-old child  were among those killed in the attack.

The hospital was treating 10 shooting victims, Rhee said. Gifford and four others were in critical condition.

Initial reports said the 40-year-old Democrat was killed, but officials later said she was critically wounded by a gunman outside a Safeway store shortly after 10 a.m. MT.

U.S. President Barack Obama called the attack "an unspeakable tragedy" and said that such "a senseless and terrible act of violence has no place in a free society."

Event at Safeway publicized

"It's not surprising that today Gabby was doing what she always does, listening to the hopes and concerns of her neighbours," Obama said in a nationally televised news conference. "That is the essence of what our democracy is about."

Giffords had been greeting constituents at her first "Congress on Your Corner" event this year. It was publicized on her website on Friday as a chance for people in Arizona's 8th congressional district to meet with her "one-on-one and discuss with her any issue, concern or problem involving the federal government."

Dr. Steven Rayle told CBC News how he had gone with a friend to meet Giffords at the Safeway store and that she was talking to a couple behind a table just before the shooting began.

"I proceeded around sort of a concrete post to the side of the table, and as I looked up, I saw a man shoot Congressman Giffords in the head and then he immediately began rapid fire [at] everybody who was around in the area."

The shooting ended when the suspect was tackled by two people.

"He probably would have shot other people had he not been tackled by two people," Dupnik said.


Democrat Gabrielle Giffords with her husband, Capt. Mark E. Kelly, a NASA astronaut and navy pilot from New Jersey. ((Reuters))

A MySpace page of Loughner included a "Goodbye friends" message published hours before the shooting and said, "Please don't be mad at me."

In 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's congressional district.

Giffords is married to Capt. Mark E. Kelly, 46, a NASA astronaut and navy pilot from New Jersey.

She was re-elected to her third term last November and was a member of the Arizona House and Senate before going to Washington.

Giffords was elected to Congress amid a wave of Democratic victories in the 2006 election. The former state legislator won a narrow victory against a Tea Party favourite last fall.

David Fitzsimmons, a cartoonist for the Arizona Daily Star, told CNN that Giffords is a centrist and a moderate.


Judge John Roll was one of six people killed in the shooting. ((Federal 9th Circuit Court/Associated Press))

"She is intelligent, informed, and she thought a great deal about the future of Arizona," he said.

Giffords herself has drawn the ire of the right, especially for her support of the U.S. health-care bill.

Her Tucson office was vandalized a few hours after the House vote to approve the health-care bill in March, with someone either kicking or shooting out a glass door and window. In an interview after the vandalism, Giffords referred to the animosity against her by conservatives.

Former Alaska governor Sarah Palin listed Giffords's seat as one of the top "targets" in the midterm elections because of the lawmaker's support for the health-care bill.

"For example, we're on Sarah Palin's targeted list, but the thing is, that the way that she has it depicted has the crosshairs of a gunsight over our district. When people do that, they have to realize that there are consequences to that action," Giffords said in an interview with MSNBC.


A photo of shooting suspect Jared L. Loughner from the 2006 Mountain View High School yearbook. ((Associated Press))

In the hours after the shooting, Palin issued a statement in which she expressed her "sincere condolences" to the families of Giffords and the other victims.

Newly elected House Speaker John Boehner said he was "horrified by the senseless attack."

"An attack on one who serves is an attack on all who serve," he said.

Dupnik suggested that the vitriolic political rhetoric on radio and television played a role in 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," he said. 

"The anger, the hatred, the bigotry that goes on in this country is getting to be outrageous. And unfortunately Arizona, I think, has become the capital. We have become the mecca for prejudice and bigotry."

Dupnik got emotional speaking of Roll, saying the judge had just come by to say hello to Giffords.

"One of the finest human beings I've ever met in my life," he said

Roll, 63, was appointed to the federal bench in 1991 by President George H.W. Bush.

With files from The Associated Press