For the record the US embassy was not attacked in Benghazi

It was the Consulate.
http://world.time.com/2012/09/14/u-s-consulate-attack-in-libya-said-twin-operation/
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Eastern Libya’s deputy interior minister, Wanis el-Sharef, said a mob first stormed the consulate Tuesday night and then, hours later, raided a safe house in the compound just as U.S. and Libyan security arrived to evacuate the staff. That suggested, el-Sharef said, that infiltrators within the security forces may have tipped off the militants to the safe house’s location.

The attacks were suspected to have been timed to coincide with the 11th anniversary of the Sept. 11, 2001, terrorist strike in the United States, el-Sharef added, with the militants using the film protest by Libyan civilians to mask their action.

Read more: http://world.time.com/2012/09/14/u-s-consulate-attack-in-libya-said-twin-operation/#ixzz26RRKdlm4