President Barack Obama has revealed that Congresswoman Gabrielle Giffords opened her eyes for the first time since being shot point-blank in the head five days ago.
The news brought a cascade of cheers and electrified a memorial service for the victims of the shooting rampage in Arizona which claimed six lives, including that of a nine-year-old girl.
First Lady Michelle Obama held hands with Giffords' husband, Mark Kelly, as President Obama revealed she continued to show signs of recovery.
Obama said Giffords opened her eyes a few minutes after he left her intensive care hospital room.
"She knows we are here, she knows we love her, and she knows that we are rooting for her through what is undoubtedly going to be a difficult journey," he said.
The President conceded that there is no way to know what set off Saturday's shooting rampage that left six people dead, 13 others wounded and the nation shaken. He tried instead to rally the country to use the moment as a reflection on America's behaviour and compassion.
"Those who died here, those who saved lives here -- they help me believe. We may not be able to stop all evil in the world, but I know that how we treat one another is entirely up to us," he said to a capacity crowd at the University of Arizona basketball arena.
As finger-pointing emerged in Washington and beyond over whether harsh political rhetoric played a role in motivating the attack, Obama sought to calm the nation.
"The forces that divide us are not as strong as those that unite us," he said.
Obama's appeal for civility played out against a deepening political debate. Earlier, Republican Sarah Palin, who had been criticised for marking Giffords' district and others with the crosshairs of a gun sight during last autumn's congressional campaign, had taken to Facebook to accuse pundits and journalists of using the attack to incite hatred and violence.
The president pleaded for Americans to remain civil now as they debate gun control, mental health services and the motivations of the killer.
"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," the president said.
The shooting happened on Saturday as Giffords, who represents southern Arizona, was holding a community outreach event in a Tucson shopping centre parking lot.
A gunman shot her in the head and worked his way down the line of people waiting to talk with her, law enforcement officials said. The attack ended when bystanders tackled Jared Lee Loughner (22), who is now in custody.