The grenade assault on the U.S. Consulate in Benghazi Tuesday was originally thought to have been sparked by rage over an anti-Muslim film made in the U.S.

But U.S sources now tell CNN that the operation was planned by an al-Qaeda offshoot that may have used the angry protest outside as a diversion.

The attack killed the U.S. Ambassador to Libya, 52-year-old Christopher Stevens, as well as three of his colleagues.

Libya's Ambassador to the U.S., Ali Suleiman Aujali, told CNN’s Christiane Amanpour that he had lost a personal friend in the attack.

“This is one of the saddest days in my life,” Aujali said. “He is a man who knows Libya very well, before and after [the revolution]. He was the man who stood by the Libyan people. He was the right man, in the right place, at the right time. It is a great loss for the Libyan people.”  FULL POST