It's a scene every parent fears, finding out their child's high school has been infiltrated by gunmen.
That was exactly the scene at Grand Blanc High School on Thursday morning, but it was all just a test.
Armed with bullet proof vests, earpieces and guns filled with blank ammunition, teams of law enforcement officials invaded Grand Blanc High School to perform an emergency readiness drill to test their lockdown procedures.
Teachers were told to go into full lockdown mode where they shut the blinds, locked the doors, turned off the lights and barricaded the doors.
About 40 to 50 law enforcement personnel from nine different agencies participated in two separate drills at both Grand Blanc High School campuses. It was designed to put the roughly 1,200 staff members through a mock live shooter event to help prepare them in the event a shooter invades the school.
NBC25 followed along with one of th drills performed yesterday, the raw video from the drill is above.