CARY – Cary-Grove High School junior Mike Harris was in his chorus class about 9 a.m. Wednesday when his teacher locked and barricaded the door.

Harris and his classmates sat calmly against a wall in the dark and heard what sounded like a muffled crack.

It was the first of two blanks fired from a starter pistol in the hallway as part of a “Code Red” lockdown drill to prepare students for the possibility there could be a shooter in the school. School officials fired the blanks so students could know the sound of gunfire.