U.S. President Barack Obama says the nation is still grieving and in shock from the mass shooting Saturday that killed six people and left a member of Congress critically wounded.
Mr. Obama spoke at the White House Monday, hours after leading the nation in a moment of silence to honor the victims of the attack in Tucson, Arizona
He and first lady Michelle Obama paused Monday at the White House, while staff and visitors gathered on the steps of the U.S. Capitol building. The New York Stock Exchange and other public institutions also fell silent.
Doctors treating House Representative Gabrielle Giffords say they are slightly more optimistic about her condition.
The doctors at Arizona's University Medical Center told reporters Monday there is no increase in the swelling of the brain of 40-year-old Giffords, who was shot in the head as she met with constituents outside a grocery story.
Dr. Michael Lemole said she is responding to simple commands, but cautioned that she is still not out of danger.
The alleged gunman is to appear in a federal court in Phoenix, Arizona Monday. He faces 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.
Those killed included a federal judge, one of Giffords' aides, and a nine-year-old girl.
Speaking Monday in Abu Dhabi, U.S. Secretary of State Hillary Clinton called the shooter an "extremist" and described Giffords as a "wonderful, incredibly brave young woman."
The speaker of the House of Representatives, John Boehner, said that House votes scheduled for this week are postponed. Flags at the White House and other government buildings are to be flown at half-staff for the week. Giffords' brother-in-law, International Space Station commander Scott Kelly, paused for the moment of silence with the rest of the ISS crew Monday.
Doctors said of those hospitalized, only Giffords remains in critical condition.
In several videos on the YouTube website, a person who posted under the name of the alleged shooter, 22-year-old Jared Loughner, criticizes the government and calls for a new currency. Law enforcement officials say they are investigating the videos.
Last March, Giffords was one of at least 10 House Democrats harassed for their support of the U.S. health care reform legislation. The front door of her office in Tucson was shattered in an act of vandalism.
In November, Giffords was re-elected to a third term in the House of Representatives. She was first elected to Congress in 2006.