Libyan President Mohammed el-Megarif speaks during a memorial service in Tripoli for U.S. Ambassador to Libya, Chris Stevens, and three consulate staff killed in Benghazi on Sept. 11.
Abdel Magid al-Fergany/AP
A Libyan military guard stands in front of one of the U.S. Consulate's burned out buildings on Sept. 14. The U.S. is offering new details of the attack on the consulate that killed four Americans, including Ambassador Chris Stevens.