The Wright-Patterson Air Force Base in Ohio confirmed that security forces and the fire department on Thursday responded to reports of an active shooter in the base’s hospital building after a training simulation was mistaken for a real-world scenario.

“This reported incident occurred during a normal, scheduled installation exercise which included an Active Shooter scenario at separate location in Area A,” the base posted on its Twitter account. “Upon investigation, it was determined that the incident at the MTF was not an actual Active Shooter incident.”