BENGHAZI, Libya (AP) — The attack that killed four Americans in Libya, including the U.S. ambassador, was an organized two-part operation by heavily armed militants that included a precisely timed raid on a supposedly secret safe house just as Libyan and U.S. security forces were arriving to rescue evacuated consulate staff, a senior Libyan security official said on Thursday.

The attacks Tuesday night were suspected to have been timed to mark the 9/11 anniversary, eastern Libya’s deputy interior minister said.