WASHINGTON, DC - JANUARY 10th: A crowd including members of Congress and their staff gathered on the East Steps of the House of Representatives for a national moment of silence in honor of the victims of Saturday's mass shooting in Tucson, Arizona.   

President Barack Obama called on the nation to observe a moment of silence today at 11:00am (ET) in honor of the six people killed and at least 13 others wounded including U.S. Rep. Gabrielle Giffords (D-AZ) when a gunman opened fire at a public event held at Tucson Safeway supermarket.