Christopher Stevens, newly appointed U.S. ambassador to Libya, shakes hands with Libyan National Transitional Council (NTC) chairman Mustafa Abdel Jalil (R) after presenting his credentials during a meeting in Tripoli, in this June 7, 2012 file photo. Stevens and three other embassy staff were killed in a rocket attack on their car, a Libyan official said, as they were rushed from a consular building stormed by militants denouncing a U.S.-made film insulting the Prophet Mohammad. Gunmen had attacked and burned the U.S. consulate in the eastern city of Benghazi, a centre of last year’s uprising against Muammar Gaddafi, late on September 11, 2012, killing one U.S. consular official. Picture taken June 7, 2012. REUTERS/Ismail Zitouny/Files