ANNISTON ARMY DEPOT, Ala. -- It all began with a post in a comment on Facebook - a threat to the installation made by a disgruntled employee.

Though this Facebook comment was just an element in Anniston Army Depot's Annual Protection Exercise, the insider threat it portrayed is something installation security personnel always watch for.

"The depot's internal risk assessment named insider threats as one of the top five threats to the installation," said Don Evans, an emergency manager with the Depot Operations Office.

The 2015 APE was a full-scale exercise, practicing the responses of the depot's Directorate of Emergency Services, Intelligence Security Management Office and the entire Emergency Operations Center team, which consists of employees from nearly every depot organization.

"The exercise's intent was to have a realistic scenario built with sufficient objectives for all first responders, emergency management, law enforcement, hazardous materials personnel, medical personnel and off-post agencies," said Brandon Whitman, a mobilization, plans and operations specialist for the Depot Operations Office who helped to design the exercise.

As the scenario unfolded, the employee who threatened the installation on Facebook came to work with a bomb in his car, exploding it at the checkpoint when his car was selected for random screening.

Though all aspects of the scenario were fictitious, the purpose of the exercise was to give each organization and agency, both on and off depot, the confidence that an insider threat would be caught and neutralized, should one ever occur.

The entire scenario was observed and evaluated by independent parties from the Department of Homeland Security.