President Barack Obama and First Lady Michelle Obama observe a 'moment of silence' on the South Lawn at the White House in Washington, DC, on January 10, 2011 to honor the victims of a shooting at an Arizona political event that left people six dead. Meanwhile, doctors were cautiously optimistic about the recovery of the shooter's principal target, US congresswoman Gabrielle Giffords, who was shot in the head by the would-be assassin.