President Obama will lead the nation in a moment of silence on the South Lawn of the White House at 11 a.m. this morning. "It will be a time for us to come together as a nation in prayer or reflection, keeping the victims and their families closely at heart," Obama said in a statement. After the silence, he'll answer questions about the shooting of Arizona Rep. Gabrielle Giffords and 19 others in the parking lot of an Arizona shopping mall on Saturday. Today the NY Times and other news outlets are piecing together the chain of events from when 22-year-old Jared Lee Loughner allegedly opened fire and when he was taken into custody.

After briefly waiting at the end of a long line to speak with Giffords at a "Congress on Your Corner" event, Loughner allegedly cut the line and advanced on the congresswoman with his Glock semiautomatic. "When he was about four feet from her, he fired at her head," Giffords's aide Mark Kimble told the Times. "Then he started shooting at the people, maybe a few dozen, waiting to talk to her. He kept shooting as he walked away." But when the shooter tried to insert a second clip into the firearm, it jammed, giving bystanders an opportunity to neutralize him. According to AZCentral.com, Patricia Maisch, who was waiting on line to see Giffords, grabbed the clip, and Roger Salzgeber, Bill Badger and Joseph Zamudio subdued Loughner.

The shooting lasted approximately fifteen seconds. Within minutes, first responders from a nearby firehouse were at the scene, and the Times reports that paramedics "swept through the carnage and performed a bloody triage, leaving behind Judge [John] Roll and at least four others who were definitely dead and sending the most gravely wounded, Ms. Giffords at the head of that list, to local hospitals in a march of ambulances and helicopters." Giffords remains in critical condition, but doctors are "cautiously optimistic" about her progress.

"We're still within the window where it could go either way," said Dr. G. Michael Lemole Jr., chief of neurosurgery at University Medical Center, adding that the first 72 hours following such a traumatic injury are the most critical. According to Kimble, the bullet entered the top of her head and traveled out the back. He told AZCentral.com yesterday, "It's the best place you can be shot... It didn't cross the centerline of the brain, which is crucial." Kimble added that the major concern now is swelling of the brain.

Three other victims shot were in serious condition Monday morning and doctors said six were in fair condition. The AP reports that Loughner has been charged with one count of attempted assassination of a member of Congress, two counts of killing an employee of the federal government and two counts of attempting to kill a federal employee. More charges are expected.