WASHINGTON (AP) -- President Barack Obama has presided over a national moment of silence for severely injured Arizona Rep. Gabrielle Giffords and the people who were killed during an assassination attempt against her.

On the White House South Lawn, Obama was joined by first lady Michelle Obama and White House staff members on a cold morning.

The moment was marked at the U.S. Capitol and elsewhere around a nation still coming to grips with the tragedy.

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Giffords is in intensive care at a Tuscon hospital after being shot in the head at close range. Among the five others killed were Arizona's chief federal judge, a 9-year-old girl and one of Giffords' aides.

Prosecutors have charged a 22-year-old Jared Loughner on a series of counts, including attempted assassination of a member of Congress.

President Barack Obama's statement about the shooting of Rep. Gabrielle Giffords, D-Ariz., in Tucson on Saturday:

This morning, in an unspeakable tragedy, a number of Americans were shot in Tucson, Arizona, at a constituent meeting with Congresswoman Gabrielle Giffords. And while we are continuing to receive information, we know that some have passed away, and that Representative Giffords is gravely wounded.

We do not yet have all the answers. What we do know is that such a senseless and terrible act of violence has no place in a free society. I ask all Americans to join me and Michelle in keeping Representative Giffords, the victims of this tragedy, and their families in our prayers.