Marietta High School students weren't in school Thursday, as teachers spent the day learning how to deal with the nightmare possibility of a mass murderer on campus.

It was not unlike the "duck and cover" drills educators practiced a generation ago. Only then, they were protecting themselves and their students from the horror of a nuclear attack by the Soviet Union.

Thursdsay, duck and cover had a new meaning: hide in the event of an active shooter on campus.

"In the event that should happen, you don't want to be going, 'Oh, crap, what do I do now?'" Grivett told about 200 Marietta High School teachers, staff members and administrators.

It was a sobering assessment of what adults should do and what they can expect in an active shooter situation like the one that cost so many lives at Sandy Hook Elementary School in Newtown, CT, last month.

Grivett warned teachers to lock themselves and their students away from danger. Block the door. And don't expect help from first responders because they are on scene to kill the person who is trying to kill them.

Teachers attending the briefing said they are sad they even have to train for such an eventuality – but they understand that this is nothing less than a sign of the times.