After an hours-long lockdown, the U.S. Navy confirmed that no shooting took place Thursday morning at the Washington Navy Yard, after reports of an incident there.
In a press conference late Thursday morning, Washington Mayor Muriel Bowser said that a Navy Yard employee reported at approximately 7:29 a.m. that "she may have heard gunshots in the facility."
After a lengthy police and federal law enforcement sweep, "there's no evidence of gunshots, there's no evidence of a shooter, and there's no evidence of any victims today," Bowser said.
D.C. Police Chief Cathy Lanier will host a meeting to examine law enforcement response.
Navy Adm. Dixon Smith said at the press conference that the Yard remained in lockdown as police finished up a final sweep of building 197, where the incident was reported; it had been locked down since just before 8 a.m. He expected to open up the Yard after the walk-through was completed at approximately 11:30 a.m.
In September 2013, a gunman killed 12 and injured three others at the Navy Yard before being shot and killed by Washington Metropolitan police. The shooting occurred in building 197.
"We've learned a lot over the last couple of years, we've exercised hard," Smith said. "We're going to review this again to see what went right, and what we can continue to improve upon to improve our procedures in the future."
Thursday morning's incident comes almost a week after the FBI, the Department of Homeland Security, and the National Counterterrorism Center warned of potential terrorist threats around the Fourth of July weekend. Police in several cities responded to the notice by boosting security measures.
But despite those warnings, Lanier said the police response was no different Thursday from what was done two years ago during the last Navy Yard shooting.
"I think it has nothing to do with the increased threat level," she said. "That's what we do every day here."
Lanier said there's no evidence that the reports were a "malicious hoax," and that the employee who called in the initial reports was following standard procedure. She confirmed reports that a surveillance video showed two men climbing a fence close to the building early Thursday. Officers have pulled all video but have "no concerns" about it at this time, Lanier said.
The Navy Yard was on lockdown since just before 8 a.m. as police continued their investigation.
The U.S. Navy confirmed on Twitter at 7:59 a.m. that the building complex in Southeast Washington had been placed on lockdown, but not the exact nature of the incident.
NBC News and the Associated Press said early on that shots were reported at the Yard. Shortly after 10 a.m., the AP reported that no shots were fired at the military base, citing a law enforcement official. WUSA reported that D.C. fire officials said no injuries were reported.
Navy spokesman Chris Johnson could not initially confirm to National Journal that no shooter was spotted, only that an active investigation is in place. He said that employees inside building 197 had been evacuated. According to a Navy tweet, a Naval Criminal Investigative Service investigation is still ongoing.
Police blocked streets in the base's vicinity as officers, emergency medical crews, and the FBI descended on the area. M Street was closed between South Capitol Street and 11th Street Southeast. Helicopters circled the scene Thursday morning, and police swept and cleared the nearby Navy Yard Metro station.
For those who remember the Navy Yard shooting two years ago, the false alarm still stirred up the trauma that hit the same building in 2013.
"My heart dropped. I almost came to tears," says Brent Whelan, who worked in building 197 in 2013.
Two years ago, he had nearly entered the building when he saw colleagues rushing out. "Something happening today, it really hits close to home," Whelan said.
"The response brings it all back," says Liliana Houndershell, who also worked in 197, but had taken her first personal day in 11 years on the morning of the shooting.
Whelan and Houndershell sat on a median on M Street just outside of Navy Yard, hoping for the best, but with the memory of the last tragedy still fresh. While both said they underwent mandatory trauma counseling and participated in group therapy sessions with coworkers, the emotion was still rushing back.
"You think you are past it and you're not," Houndershell said. "I thought I was good."
Capitol Police said Thursday it has boosted security on the Capitol grounds in response to the reported incident. "We have additional units in the field deployed strategically around the Capitol complex, as the situation dictates, while remaining available to continue to provide mutual support at the Navy Yard," Capitol Police spokeswoman Lt. Kimberly Schneider said.
Lanier said that tourists visiting Washington for the holiday weekend are coming into a city that's "very well-prepared" safety-wise, with close coordination between local and federal law enforcement.
"I think people should feel very comfortable that this type of response does happen," she said.
Lauren Fox, Rachel Roubein, and Dustin Volz contributed to this article