Around 3 p.m. Thursday, the base posted the following explanation on their Facebook page:
The base is in a REAL WORLD active shooter posture out of an abundance of caution. During a pre-planned exercise, it appears that a worker using a jackhammer in the AGE yard area produced sounds that were reported as possible shots fired. However, to ensure the safety of base personnel, the incident is being treated as a full active shooter report until Security Forces can 100 percent confirm that there is no threat to the base.
Then, around 3:35 p.m., the base gave an "all clear," and confirmed that normal operations were again underway.