UPDATE: Senior law enforcement officials confirmed there was never an “active shooter” at Joint Base Andrews on Thursday, NBC News’ Pete Williams reported.
Williams said the officials told him the confusion stemmed from a planned "active shooter" drill on Thursday morning.
"There were two personal walking across the base carrying rifles…someone in the medical center on the third floor looking out the window saw that and phoned in that there was a shooter on the base," he reported.
Sources: No active shooter at Joint Base Andrews https://t.co/DcKxp2ddzY— MSNBC (@MSNBC) June 30, 2016
Joint Base Andrews in Camp Springs, Maryland, is on lockdown after a "report of an active shooter."
The base advised all personnel to “shelter in place."
JBA is currently on lockdown due to a report of an active shooter. All personnel are directed to shelter in place. More info as it comes.— Joint Base Andrews (@Joint Base Andrews) 1467292587.0
As of 9:36 a.m. ET, the incident was described as "ongoing."
Homeland Security Secretary Jeh Johnson addressed the situation on social media, calling the incident an "unfolding situation."
The incident is ongoing at the Malcolm Grow Medical Facility. First responders are on-scene now. All personnel continue to shelter in place— Joint Base Andrews (@Joint Base Andrews) 1467293622.0
Due to the serious nature of this report, the base is reacting to ensure the safety of all personnel.— Joint Base Andrews (@Joint Base Andrews) 1467295151.0
NBC Washington reported that there may have been a planned active shooter exercise on Thursday.