"The violence, though, also had spontaneous elements. Anger at the video motivated the initial attack. Dozens of people joined in, some of them provoked by the video and others responding to fast-spreading false rumors that guards inside the American compound had shot Libyan protesters. Looters and arsonists, without any sign of a plan, were the ones who ravaged the compound after the initial attack, according to more than a dozen Libyan witnesses as well as many American officials who have viewed the footage from security cameras.
The Benghazi-based C.I.A. team had briefed Mr. McFarland and Mr. Stevens as recently as the day before the attack. But the American intelligence efforts in Libya concentrated on the agendas of the biggest militia leaders and the handful of Libyans with suspected ties to Al Qaeda, several officials who received the briefings said. Like virtually all briefings over that period, the one that day made no mention of Mr. Abu Khattala, Ansar al-Shariah or the video ridiculing Islam, even though Egyptian satellite television networks popular in Benghazi were already spewing outrage against it."
http://www.nytimes.com/projects/2013/benghazi/#/?chapt=0
