By Tim Gaynor and Peter Henderson
TUCSON, Arizona (Reuters) - Doctors were cautiously optimistic on Sunday about the condition of U.S. congresswoman Gabrielle Giffords after a man shot her in the head and killed six people at a public event in Arizona.
The shootings of Giffords and 19 other people in Tucson on Saturday fuelled debate about extreme political rhetoric in America after an acrimonious campaign for congressional elections last November.
The 22-year-old suspect, Jared Lee Loughner, was due to face formal charges in federal court on Sunday as investigators sought a motive and looked for a possible accomplice.
"It appears that the target was the congresswoman," FBI Director Robert Mueller told a news conference.
Public officials should be on alert but there was no information to suggest a specific threat, he said.
Giffords, a 40-year-old Democrat, was in critical condition but was able to follow simple commands, such as holding up two fingers when asked, doctors at University Medical Centre in Tucson said.
A single bullet travelled the length of her brain on the left side, hitting an area that controls speech functions. Given the devastating wound, doctors said they were uncertain about the extent of brain damage she had suffered.
Giffords has been put into a pharmaceutical coma but was being woken frequently to check her progress.
"There are obvious areas of our brain that are less tolerant to intrusion," said Dr. Michael Lemole. "I don't want to go down the speculation road but at the same time we're cautiously optimistic."
RAMBLING MANIFESTO
Gun violence is common in the United States but political shootings are rare.
The suspect opened fire with a semi-automatic pistol at point-blank range outside a supermarket, killing six people including U.S. federal judge John Roll and a 9-year-old girl. Fourteen people were wounded.
Pima County Sheriff Clarence Dupnik said a wounded woman clawed away an ammunition magazine from the gunman, possibly preventing even more people from being shot. The gunman managed to reload his Glock pistol but the fresh magazine would not work and the suspect was then tackled by two men.
Arizona police released a photo of another man sought for questioning who was seen at the shopping centre. He is white and appears to be 40 to 50 years old but Dupnik said he was not believed to be directly involved in the shooting.
The violence shocked politicians in Washington, where Congress postponed a vote on healthcare reform later this week. Some Democrats were quick to say a shrill climate of political vitriol might have played a role.
"We are in a dark place in this country right now and the atmospheric condition is toxic," Democratic Representative Emanuel Cleaver told NBC's "Meet the Press" program.
But Jon Kyl, a Republican senator from Arizona, cautioned against a "rush to speculate."
"We really don't know what motivated this young person, except to know he was very mentally unstable," Kyl said on the "Face the Nation" show on CBS.
Police seeking a motive for Saturday's rampage were looking at a rambling Internet manifesto left by Loughner or someone writing under that name. There was no coherent theme to the writing, which accused the government of mind control and demanded a new currency.
The U.S. Army confirmed the suspect attempted to enlist in December 2008 but was rejected for unspecified reasons.
House of Representatives Speaker John Boehner ordered flags at the U.S. Capitol in Washington lowered to half staff in memory of the victims. He said the incident was a reminder that public service comes with a risk.
POLITICAL FALLOUT
Lawmakers in Washington put off their agenda for this week, including a vote on the repeal of President Barack Obama's contentious healthcare overhaul.
The new Congress convened last week after the November 2 elections in which the Republican Party won control of the House and reduced the Democratic majority in the Senate.
The U.S. Capitol Police cautioned members of Congress "to take reasonable and prudent precautions." Still, most lawmakers are largely unguarded outside the Capitol, except the leaders of the House and Senate, who have security details.
Giffords warned previously that the heated rhetoric had prompted violent threats against her and vandalism at her office. Mueller said the suspect had attended a public event held by Giffords in 2007.
In an interview last year with MSNBC, Giffords cited a map of electoral targets put out by Sarah Palin, a Republican former Alaska governor and prominent conservative, that had each marked by the crosshairs of a rifle sight.
After the shooting, the graphic was removed from Palin's website and she offered condolences on a posting on Facebook.
A Palin aide, Rebecca Mansour, told conservative radio host Tammy Bruce of the graphic: "We never, ever, ever intended it to be gun sights. It was simply crosshairs like you'd see on maps ... a surveyor's symbol."
YOUTUBE VIDEOS
Mueller said "hate speech and other inciteful speech" presented a challenge to law enforcement officials, especially when it results in "lone wolves" undertaking attacks.
In several videos on the Internet site YouTube, a person with the name Jared Lee Loughner criticizes the government and religion. It was not known whether he was the same person as the suspect.
"The government is implying mind control and brainwash on the people by controlling grammar," the man says. "No! I won't pay debt with a currency that's not backed by gold and silver! No! I won't trust in God!"
In a biographical sketch on the site, the man writes that he attended Tucson-area schools and says his favourite books include Adolf Hitler's "Mein Kampf," Karl Marx's "Communist Manifesto" and Ken Kesey's "One Flew Over the Cuckoo's Nest," which is set in a mental asylum.
Giffords, married to NASA astronaut Navy Captain Mark Kelly, is seen as a rising star in the Democratic Party. She narrowly defeated a conservative opponent and was one of the few Democrats to survive the Republican sweep in swing districts in November's elections.
Arizona has been at the centre of a political firestorm in the past year, symbolizing a bitter partisan divide across much of America.
The spark was the border state's move to crack down on illegal immigration last summer, a bill proposed by conservative lawmakers and signed by the state's Republican governor, Jan Brewer.
Most Arizonans supported the crackdown but opponents and many in the state's large Hispanic community felt it was unconstitutional and would lead to discrimination. Giffords said it would not secure the border or stop drug smuggling and gun running.
(Additional reporting by Andy Sullivan, Richard Cowan, Tabassum Zakaria and Kim Dixon in Washington, David Schwartz in Phoenix and Dan Whitcomb in Los Angeles; Writing by Steve Holland; Editing by John O'Callaghan)
