Andrews Air Force Base, MD -- Authorities say there is not an active shooter and the all clear has been given at Joint Base Andrews.
Sources say someone at the Malcolm Grow Medical Facility looked out window and saw people with guns and BDUs. They called authorities, not realizing that what they were seeing was a pre-scheduled drill.
Conflicting reports about what was happening then began to circulate at the base, on social media and among the news media.
Rodney Smith, the patient advocate at the Andrews medical facility, said an active-shooter exercise was scheduled for Thursday morning, and then he was told it was a "real-world" situation. He said he was on lockdown and didn't have any more information.
"First it was an active-shooter exercise. Then it came back 'real world,'" Smith said by phone Thursday morning.
After a hour long lockdown, officials did not find any active shooter and lifted the lockdown.
Joint Base Andrews is about 20 miles outside the nation's capital and is home to Air Force One.
Vice President Joe Biden was scheduled to leave from Andrews on Thursday morning, but his trip for a campaign appearance in Columbus, Ohio was delayed by the lockdown.