Correction. The Information Security Officer was Sean Smith, who served in the U.S. Air Force as a Staff Sergeant.
The other two were embassy security personnel, Glen Doherty and Tyrone Woods, both former Navy SEALs.
They weren't Embassy security personnel. They were contracted by another agency to perform certain unspecificed duties in Benghazi. They were not responsible for the security of Embassy Tripoli or the US mission in Benghazi.