U.S. Officials Investigating “Mystery Drone” Incident Over Barksdale Air Force Base That Prompted Security Alert

"Sightings of an unmanned aerial system over Barksdale Air Force Base (BAFB) early on Monday morning resulted in a shelter-in-place order, prompting officials to temporarily raise

the threat level at the facility.
For a short period, the base’s Force Protection Condition level was temporarily raised to FPCON Charlie, indicating an incident potentially indicative of a form of terrorist activity targeting U.S. personnel or facilities.
Postings on social media shortly thereafter indicated that the threat level had been lowered again, although no additional information on what had prompted the declaration was provided at that time." msn