Police cars and SWAT team vehicles were parked near the massive compound, covering the streets and sidewalks for blocks in every direction. Ambulances screamed to the Navy Yard, ready for the possibility of mass casualties. A helicopter circled overhead and tactical teams scrambled onto rooftops and sealed a six-square block perimeter.
"It was a clear, coordinated and convincing response to this incident,” D.C. Mayor Muriel Bowser said shortly after it all was declared a false alarm.
Lanier added, “We operate in D.C. like there is an elevated threat level at all times. We are aware of the discussion and chatter surrounding the Fourth of July events and we take that into account. We take every event here in Washington very seriously and our posture remains extremely high for all special events, and that will continue for the Fourth."
While federal law enforcement officials acknowledge that authorities are on high alert for the upcoming holiday, Lanier indicated that the quick response to this morning’s possible threat was more closely linked to the shooting the Navy Yard in 2013, when 12 people were killed by an active shooter who went through the facility, shooting former co-workers.
“We spend a lot of time on after action reports,” Lanier said. “It appears that a lot of the things we tried to correct and go better from the last incident went very, very well. Things went very smoothly, there was a well-coordinated response here.”
She added, “This turns out to be a great exercise for us, and nobody is hurt.”
Indeed, no threats was found after a complete building search this morning, although the Navy Yard remained on lockdown for several hours.
An employee heard what she thought was a gunshot and placed a call around 7:29 a.m., officials said. The call went to an internal call center inside the Navy Yard. Local police also responded to the scene, officials said.
Authorities have interviewed the employee who made the call and have no concerns about the intentions of her report.
"This is an employee that did exactly what we ask employees to do," Lanier said.
In September 2013, a lone gunman went on a shooting spree at the Navy Yard, killing 12 people. The suspect was then killed in a firefight with police.
Luis Martinez and Jack Date contributed to this report