(Story developing. Check back for updates.)UPDATE …
Officials say at least one shooter has died at the Washington Navy Yard, where several people were killed and as many as 10 were wounded, according to the AP.
A federal law enforcement official and a Defense Department official said Monday morning that a shooter had died. Both spoke on condition of anonymity because they were not authorized to discuss the ongoing investigation.
Two other officials have said they are looking into the possibility of a second shooter at the Navy Yard.
Meanwhile, an official told CBS News the number of victims could be higher because it is a “chaotic scene.” Officials have not offered publicly an exact assessment of the health of the victims.
It is also not clear whether neutralized gunman is a member of the Navy.
Police and emergency crews gathered Monday morning outside the heavily-guarded Naval Sea Systems Command Headquarters building, where the shooting was reported. To enter the building, visitors and employees must pass several checkpoints, leading to some speculation this may have been a coordinated attack by an insider or multiple insiders.
The Navy said about 3,000 people work in the building. People inside the building have been directed to stay in place.
For more, go to CBS News.
Earlier we reported …
*Police believe two shooters, including one in fatigues, have killed four people and wounded eight others at the Washington Navy Yard on Monday, throwing the region into fear and chaos during the morning commute reports The Washington Post.
At least one of the shooters is “down,” police said mid-morning, but it was unclear whether that means the suspect has been arrested or shot. They said the other suspect remains at large, and police believe they have pinned down one between the third and fourth floors of one of the buildings on the installation in Southeast Washington.
Police on the scene said at least eight civilians were shot, along with the two police officers. One is a D.C. Metro Police officer who was shot twice in the leg and was evacuated on a helicopter that took off from a rooftop, police said. The other officer worked at the base. Except for the officer who was taken away by helicopter, all the other injured were being treated on the ground, police said.
A Navy Yard employee reached by telephone shortly before 10 a.m. said employees are still being told to shelter in place. She did not hear the shots, but described sirens, SWAT teams, Marines and a helicopter responding.
The U.S. Navy said that three shots were fired around 8:20 a.m. at the Naval Sea Systems Command Headquarters building, where about 3,000 people work.
In a number of tweets from the base, employees expressed their fright. One tweet said people were stuck on the fourth floor of the headquarters building, while the shooter was firing from the third floor. Others wrote of being incredulous that a shooter could get inside the building.
Two Navy yard employees interviewed on CNN said they were fired on in a hallway by a gunman they described as a tall black man.
A woman who gave her name as Terry Durham said that as she and co-workers were evacuating, she saw a man down the hall raise a rifle and fire toward them, hitting a wall. “He was tall. He appeared to be dark-skinned,” she said.
“He was a tall black guy,” said her co-worker, Todd Brundage, who is black. “He didn’t say a word.”
One man who said he was at his desk on the second floor when the shooting began recalled hearing a loud noise “like someone dropping an old metal desk.” The man, who declined to give his name, said there was a pause, then several noises close together and he realized the danger: “There’s a shooter in the building. I started walking toward the door and I heard people running down the hall.”
Employees described the chaos, as a fire alarm sounded and people shouted, “Where is he? Where is he?”
Police closed the 11th St Bridge as well as M St SE between 2nd and 4th streets SE due to the shooting. Entrances to the Navy Yard Metro station remain open.
U.S. Capitol Police confirmed enhanced security at the Capitol, but no immediate threat.
Tyler Elementary School at 10th and G streets in Southeast was on lockdown.
As helicopters circled overhead and emergency vehicles continued to rush to the scene, crowds of onlookers gathered on sidewalks and at a construction site near the Navy Yard, but police pushed them back, yelling at them to keep a distance from the grounds.
President Obama has been briefed on the situation at the Washington Navy Yard, according to a White House official who asked not to be identified because the situation was still fluid.
“The President has been briefed several times about the unfolding situation at the Washington Navy Yard by Assistant to the President for Homeland Security and Counterterrorism Lisa Monaco and Deputy Chief of Staff Alyssa Mastromanaco,” the official said. “The President directed his team to stay in touch with our federal partners, including the Navy and FBI, as well as the local officials. We urge citizens to listen to the authorities and follow directions from the first responders on site.”