Mourning the victims of Arizona shooting over the weekend which also left a lawmaker fighting for her life in hospital, US President Barack Obama has asked his countrymen to overcome their divisions and not use the occasion to turn on one another.

Cancelling all his pre-scheduled engagements, Obama accompanied by the First Lady, Michelle, travelled to Tucson in Arizona, the venue of the deadly shooting, to personally mourn the tragic incident that killed six people and injured several others, including Congresswoman Gabrielle Giffords, who is now battling for life in hospital.

“For the truth is that none of us can know exactly what triggered this vicious 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,” Obama said.

“So yes, we must examine all the facts behind this tragedy. We cannot and will not be passive in the face of such violence. We should be willing to challenge old assumptions in order to lessen the prospects of violence in the future,” Obama said in his speech before a packed auditorium of more than 14,000 people at Tucson, Arizona.

He asked his countrymen to overcome their divisions and show unity in a moment of crisis.

“What we can’t do is use this tragedy as one more occasion to turn on one another. As we discuss these issues, let each of us do so with a good dose of humility. Rather than pointing fingers or assigning blame, let us use this occasion to expand our moral imaginations, to listen to each other more carefully, to sharpen our instincts for empathy, and remind ourselves of all the ways our hopes and dreams are bound together,” Obama said.

“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 added.

Obama’s speech followed a fiercely partisan political debate which erupted over the rampage.

Some liberal commentators charged Republicans like Sarah Palin with whipping up a climate of political hate, which they say may have influenced alleged gunman Jared Loughner.

Loughner, 22, has been charged on five counts two of murder and three of attempted murder.

“After all, that’s what most of us do when we lose someone in our family especially if the loss is unexpected. We’re shaken from our routines, and forced to look inward. We reflect on the past,” he said.

“Sudden loss causes us to look backward but it also forces us to look forward, to reflect on the present and the future, on the manner in which we live our lives and nurture our relationships with those who are still with us. We may ask ourselves if we’ve shown enough kindness and generosity and compassion to the people in our lives,” he said.

Obama said when a tragedy like this strikes, it is part of human beings nature to demand explanations to try to impose some order on the chaos, and make sense out of that which seems senseless.

“Already we’ve seen a national conversation commence, not only about the motivations behind these killings, but about everything from the merits of gun safety laws to the adequacy of our mental health systems. Much of this process, of debating what might be done to prevent such tragedies in the future, is an essential ingredient in our exercise of self-government,” he noted.