Updated Mon, Sep 16, 2013 2:18 pm
UPDATE 2:17 p.m. Police say at least 12 people have died in the shootings at the Washington Navy Yard.
D.C. Police Chief Cathy Lanier said during a news conference Monday that 12 people were confirmed dead.
Lanier says people are being told to stay in their homes and out of the area as authorities search for two other possible suspects. One of the shooters has died.
The police chief says officers are searching for two other people with firearms wearing military-style uniforms.
She says there is no indication of a possible motive at this time.
UPDATE 1:30 p.m. A man who works at the Washington Navy Yard says he and some co-workers encountered a gunman this morning in a long third-floor hallway of the building where they work. Todd Brundige says the man "just turned and started firing."
Co-worker Terrie Durham says the gunman fired toward her and Brundige, but that he "aimed high and missed." She says the gunman said nothing.
Rick Mason, who's a civilian working for the U.S. Navy, says a gunman was shooting from a fourth-floor overlook in the hallway outside his office, aiming down at people in the building's cafeteria. He says he could hear the shots, but couldn't see the gunman.
Shortly after the gunfire, he says someone on an overhead speaker told workers to seek shelter -- and later, to head for the gates at the complex.
Patricia Ward says she was in the cafeteria when the shooting began. She says she heard three gunshots in a row, followed by several more. She says, "We just started running." Security officers were directing people out of the building, with guns drawn.
UPDATE 1:15 p.m. Police in Washington, D.C., are looking for two other possible gunmen, after a shooting today at the Washington Navy Yard that left six people dead.
Officials say at least four others were wounded, including a law enforcement officer. Police say a third gunman has died, though they're not saying how.
Witnesses describe a gunman opening fire from the fourth floor, aiming down at people in a first-floor cafeteria. Others say a gunman fired at them in a third-floor hallway. It's not clear whether they're describing the same shooter.
Police say the two other potential gunmen were wearing military-style uniforms, including one who was wearing a beret. The police chief says one of them had a long gun, and the other was also armed.
The shooting prompted nearby schools to be put on lockdown. And planes at Reagan National Airport were briefly grounded so they wouldn't interfere with police helicopters. Less than two miles away, security was beefed up at the U.S. Capitol, but police said there was no known threat there.
About 3,000 people work at the Naval Sea Systems Command headquarters. It builds, buys and maintains the Navy's ships and submarines and its combat systems.
UPDATE 11:17 p.m. Two officials say police are looking into the possibility of a second shooter at the Washington Navy Yard where several people were killed.
A Defense Department official and a law enforcement official spoke on condition of anonymity Monday because they were not authorized to discuss the ongoing investigation.
At least one gunman opened fire inside the Naval Sea Systems Command headquarters, where about 3,000 people work just miles from the Capitol.
Among the wounded was a D.C. police officer, according to a law enforcement official who spoke on the condition of anonymity because the person was not authorized to discuss an ongoing investigation.
At least 10 were wounded.
UPDATE 10:28 p.m. A Defense Department official says several people have been killed and as many as 10 have been wounded in a shooting at the Washington Navy Yard.
The official spoke on condition of anonymity Monday because the official was not authorized to discuss the matter publicly.
The official also says the shooter is "contained" but not yet in custody.
Earlier in the day, the U.S. Navy said it was searching for an active shooter at the Naval Sea Systems Command headquarters, where about 3,000 people work.
The exact number of people killed and the conditions of those wounded was not immediately known.
The U.S. Navy says one person is injured after a shooting at a Navy building in Washington.
Police and emergency crews gathered Monday morning outside the Naval Sea Systems Command Headquarters building, where the shooting was reported.
The Navy says three shots were fired and that that about 3,000 people work in the building. People inside the building have been directed to stay in place.
Naval Sea Systems Command is the largest of the Navy's five system commands and accounts for a quarter of the Navy's entire budget.
It builds, buys and maintains the Navy's ships and submarines and their combat systems.
Police from multiple local and federal agencies were responding along with SWAT crews.