CORONADO, Calif. - Sailors at Naval Amphibious Base Coronado were engaged in a training scenario along with police Wednesday that included mock-terrorists storming through the base entrance.

According to Navy officials, during the annual "Citadel Shield" exercise, intruders are tasked with eliminating guards to get on base and making their way into a building, where several people are then held hostage.

The Navy said it wants to make it feel as real as possible, giving sailors a chance to react to possible threats.

The exercise also included injury scenarios where gunshot wounds were treated.

During the drill, supervisors wearing orange vests watched and evaluated the sailors as the situation played out.

According to officials, the judges were targeting areas for improvement, which the Navy says is a crucial part in making sure the base is really prepared for everything.

10News received reports from residents throughout San Diego who reported hearing a mysterious boom that some thought may have come from the drill. However, Navy officials on Coronado say they heard the sound as well, and it didn't come from the training exercise.

Witnesses at the scene said the sound came from offshore.