It happened just before 6 a.m. when police got a call for possible shots fired and glass breakage. Police blocked several entrances to the high school campus while officers searched the building.
Officers searched for about 2 hours before giving the "all clear." Teachers and buses carrying students were diverted to a nearby Dierbergs parking lot while officers secured the building.
At 8 a.m., buses rolled againand classes will start at 8:50 a.m.
The Kirkwood superintendent said janitors inside the building heard a crashing noise that sounded like shots and quickly followed protocol and called police. But that crash was a possibly a box of light bulbs that fell and broke.
Kirkwood along with several other police agencies responded to the school and classes were delayed until authorities could ensure the safety of the building.