WASHINGTON: A shooting rampage Monday at a US naval base in the heart of Washington claimed at least 12 lives, including the unidentified gunman, while another possible suspect was still at large, police said.
The shooting sparked a massive show of force as police and federal agents surrounded the Navy Yard, cordoning off streets only blocks from the US Capitol, home of Congress.
US officials gave no indication of any link to terrorism while police said the motive for the attack on the naval installation was unknown.
"At this hour, it appears that we have at least 12 fatalities," Washington DC police chief Cathy Lanier told a press conference.
She initially said there were two other potential shooters on the loose, but her deputies later said one of them had been cleared.
Police were searching for a black male aged 40 to 50 clad in an olive-drab, military-style uniform, she said.
With schools nearby on lockdown and streets blocked off, Lanier warned residents near the Navy Yard that police were still conducting an "active search."
"Stay in your homes and stay out of the area," she said.
With conflicting reports about the incident swirling online, a clear picture of exactly what had happened at the naval installation had yet to emerge.
Earlier media reports had said a shooter allegedly barricaded himself in a room in a headquarters building.
It was unclear how one or more attackers could have penetrated the heavy security that surrounds the Navy Yard, which is located on the Anacostia River, less than two miles (three kilometers) from the Capitol.
The description of the other potential shooter perhaps wearing a uniform raised the possibility that the attack was carried out by insiders who had military passes to enter the facility.
The police chief confirmed a Washington DC police officer was among those injured in the rampage, and hospital officials said he was in critical condition with wounds to his legs.
One employee at the Navy Yard, Patrica Ward, said she had just paid for her breakfast at a cafeteria when shots rang out.
"I was waiting for my friend to pay when we heard the gun shot. It was three gun shots straight in a row, 'pow-pow-pow,'" she told reporters.
"Three seconds later it was 'pow-pow-pow.' So it was like a total of seven gun shots. And we just started running."
The guard "told all of us to just run, to get away as fast as you can."
She said employees do not have to pass through a metal detector when they enter the building.
Police blocked off intersections around the Navy Yard as military troops in uniform stood guard at street corners and patrol boats moved in near the site along the banks of the Anacostia river.
Crowds of onlookers stood on sidewalks watching the drama unfold, as helicopters swarmed overhead.
The US Navy on its Twitter account said "several" people had been injured, while police officers told local media up to 10 people had been wounded.
Several schools in the area were on lockdown as a precaution, authorities said, and flights out of the nearby Reagan National Airport were delayed.
The Navy said at least three shots were fired at 8:20 am (1320 GMT) in the headquarters building of the Naval Sea Systems Command.
About 3,000 people work at the headquarters, which oversees the building and buying of warships and combat systems.
The site, which includes a naval history museum, dates back to the early 1800s, starting out as a shipbuilding center.
The complex also has a residence which serves as the home of the four-star chief of the US Navy, Admiral Jonathan Greenert.
The White House said President Barack Obama had been briefed several times about the shooting spree by top security and counter-terrorism officials.
"As this investigation moves forward, we will do everything in our power to make sure whoever carried out this cowardly act is held responsible," Obama said.
The US president lamented that America was confronting "yet another mass shooting" and said service men and women should not have to expect to confront danger at home.