Article Photos: US investigates: Attacks coordinated to mark 9/11?



White House workers walk on the roof of the White House after lowering the flag to half staff for the death of U.S. ambassador to Libya Christopher Stevens, Wednesday, Sept. 12, 2012 in Washington. (AP Photo/Evan Vucci)

White House workers walk on the roof of the White House after lowering the flag to half staff for the death of U.S. ambassador to Libya Christopher Stevens, Wednesday, Sept. 12, 2012 in Washington. (AP Photo/Evan Vucci)