Muzzles flashed and victim's fell.

What seemed like chaos aboard Marine Corps installation Camp Lejeune Thursday was an organized active shooter drill.

The drill was planned for four months. Three shooters armed with pistols and blank cartridges stormed the lawn of headquarters. In a manner of minutes the initial gunfire had ceased and two shooters had ran into a nearby building.

Police responded first to the drill, followed by emergency first response and later hospital staff laid hands on the mock victims. Each agency in the military had a roll in the drill.

Active shooter drills are intended to help those on base prepare for a real shooting situation.

"As you can see in the world today there are catastrophic events that take place everyday. We have to be able to respond to those appropriately," Major Tito Jones said. "We have to dust off our techniques, tactics, and procedures to make sure we are able to respond adequately to something of that nature."

The drill's timeliness to Wednesday's shooting at Fort Hood was mere coincidence. These drills are held every year.

"It underscores the seriousness about which we take this training," Public Relations official for Camp Lejeune, Nat Fahy said.

All 21 victims were taken to the base's hospital and treated for fake, but realistic looking, wounds.

In all, the drill took 6 hours from start to finish.