|The US president visited victims of the shooting at a Tucson hospital before the memorial service [Reuters]
Barack Obama, the US president, has called on Americans to unite regardless of their political colours as he paid tribute to the victims of a deadly shooting at a political event in the state of Arizona.
In his eulogy at a crowded indoor sports arena on Wednesday, Obama called for a more civil public discourse and warned that Americans should not turn on each other as they seek to understand what triggered the attack outside a supermarket in the city of Tucson.
"Bad things happen, and we must guard against simple explanations in the aftermath," he said.
Much of the media focus following the shooting, which left six people dead - including a nine-year-old girl and a federal judge - has been on whether the divisive political atmosphere in the US played a part in motivating the suspected attacker.
Obama said that no one could know what triggered the attack.
"None of us can know with any certainty what might have stopped those shots from being fired, or what thoughts lurked in the inner recesses of a violent man's mind," he said.
Jared Loughner, 22, is in custody after Saturday's shooting facing five charges including murder and attempted murder.
But the president expressed a hope that the events of recent days would "usher in more civility in our public discourse".
"At a time when our discourse has become so sharply polarised - at a time when we are far too eager to lay the blame for all that ails the world at the feet of those who think differently than we do - it's important for us to pause for a moment and make sure that we are talking with each other in a way that heals, not a way that wounds," he said.
"What we can't do is use this tragedy as one more occasion to turn on one another."
Gabrielle Giffords, a Democrat congresswoman and the apparent primary target of the shooting, was among 14 people injured after a man opened fire with a semi-automatic pistol.
Giffords held on to her seat in November's midterm elections after a bitter race that saw violent threats against her and vandalism at one of her offices
Sarah Palin, the former Republican vice-presidential candidate, had identified the congresswoman's Arizona district one to target in her "Take Back the 20" campaign, which included a map of the US with crosshairs on congressional districts of Democratic candidates she had singled out for defeat.
On Wednesday, Palin hit out at attempts to link political rhetoric by her and her "Tea Party" movement to the attack.
"Acts of monstrous criminality stand on their own. They begin and end with the criminals who commit them," she said.
"Especially within hours of a tragedy unfolding, journalists and pundits should not manufacture a blood libel that serves only to incite the very hatred and violence they purport to condemn. That is reprehensible."
Al Jazeera's Patty Culhane, reporting from Tucson, said Obama's speech set a new marker for how politics is carried out during the rest of his presidency.
"From here on out I think everything he does will be measured by the pundits against this incredible speech he gave here tonight," she said.
"We've moments in the past where mass tragedies have led to legislation but we haven't seen a change in the tone in Washington.
"It really does seem that every year [the political rhetoric] gets a litte bit more heated, a lit bit more angry, a little bit more violent ... so the questions remains to be seen if that is now going to stop."
Before addressing the memorial service, Obama visited Giffords at the University Medical Center where she in critical condition after being shot in the head.
"The president wanted to begin this solemn trip by stoppingfirst at the hospital where Congresswoman Giffords and others continue to recuperate," Robert Gibbs, the White House spokesman, said.
Obama talked to some of the medical staff treating Giffords and the 13 others wounded in the attack, as well as meeting the families of some of the six who died.
Speaking as Giffords' husband, Mark Kelly, watched from the front row of the memorial service, Obama called the congresswoman by her nickname "Gabby" and said that she had opened her eyes .
"She knows we love her," he told the 14,000 people gathered to hear him pay tribute to the victims of the shooting.
Al Jazeera and agencies