At the time, there were about 100 workers inside NASIC, which is a 24-hour operation.
“The folks inside the building did exactly what they were supposed to do. They barricaded themselves in, turned the lights off, closed the windows, did all the things that we train,” Miller said.
The colonel praised all involved, from the pair who reported the incident to the security forces and law enforcement and other partners in the community.
“Fortunately after both the primary and the secondary sweep nothing was found,” he said.
The lockdown was in place for about four hours before the all-clear was announced around 1:30 a.m. Friday.
An investigation is underway, Miller said, to determine what the individuals heard that they thought was a gunshot.
Investigators also will look at any lessons that can be learned from the incident to apply to future training and procedures.