WASHINGTON — A shooter who had engaged police in a running firefight through the sprawling Washington Navy Yard was shot and killed Monday, as officials continued to search the base for a possible second shooter, law enforcement officials said.

At least four people in addition to the shooter were killed and at least eight were wounded in the rampage that began at approximately 8:20 a.m. at the Navy Yard, a huge complex of building located along Washington’s Anacostia River waterfront.

Roughly two hours later, witnesses at the base reported hearing shots fired. A senior law enforcement official said a suspect, who had been barricaded in a room in the Naval Sea Systems Command headquarters building, had been shot and killed.

Authorities continued to search buildings in the area, said the official, but no shots have been fired since the gunman was killed.

“There could be more than one shooter. That’s possible. We’re receiving conflicting reports,” said Lt. Greg Raelson, a Navy spokesman.

PHOTOS: At the scene of Navy Yard shooting

A federal law enforcement official monitoring the situation said the conflicting reports of more than one gunman are coming from a situation where a “second building” is being checked for reports of shots fired. The official said most of the shooting occurred at the Sea Systems Command building, and that tactical SWAT squads were now canvassing the second building.

“We won’t know what we have until we clear that other building,” said the source, who asked not to be identified because of the fluid situation.

In internal alerts, police described the shooter as a six foot tall black male adult, said the official.

Officials have ramped up security in all federal buildings in the Washington area. As a precaution, U.S. Capitol Police have added personnel and increase security measures in the Capitol Building.

As helicopters hovered above the base, first lowering stretchers to airlift victims to local hospitals and later circling the base in an apparent search effort, air traffic was briefly grounded at the nearby Reagan National Airport. Several area schools were put on lockdown.

Patricia Ward, a logistics management specialist, was in building 197 when the shooting started. She said she was in the lobby using the ATM machine when she heard three shots. She said she started “panicking.” She said she didn’t know what was going on. Then she heard four more shots. A security guard with a gun drawn told them to run, she said. “I just ran. I thought of my family and I just ran.” Someone had pulled the fire alarm.

Ward said that to get into the building, a person has to scan an ID card and put his or her bags through a metal detector. She added there is no metal detector for the body. She said that may be how the shooters got weapons in.

"An active shooter was reported" at roughly 8:20 a.m. inside the headquarters building, according to the Navy.

A D.C. police officer and a base security officer were among the reported victims.

About 3,000 people, both civilian and military, work at the Naval Sea Systems Command Headquarters.

Navy Capt. Danny Hernandez said he was in an adjoining Navy Yard building when the shooting started.

“Everybody rushed in,” to the building where he was, and security guards locked down the facility.

“It was pretty orderly,” he said.

Rodriguez said in a cellphone conversation that the lockdown was still in effect.

"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 Mastromonaco," the spokesman 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."

But guns are banned from being carried outside the home there!

Don't be dumb - this is a Federal installation.

WASHINGTON — Federal officials have identified a 34-year-old man from Fort Worth, Texas, as the shooter responsible for killing 11 people at the Washington Navy Yard on Monday.

The shooter, who was killed by police during a gun battle some two hours after the initial shootings, was a government civilian contractor new to the Washington, D.C., area, said a law enforcement official speaking on condition of anonymity to discuss the investigation.

So the guns magically teleported through DC? People on base aside from MP's are allowed firearms?

No and no.

However is it realistic? I'm not saying its not, but there is a reason they have one line going into the base for regulars with IDs that only gets searched randomly and one for strangers that gets searched all the time. It is a workplace that lots of people need to get into and out of in a timely fashion in order to get their jobs done. The Opposite of Security is Accessibility. Odds are the guy was check in with his ID, but his vehicle wasn't searched since he was one of those regulars. It will be interesting to see if we can determine what his motives were and how he got his posting/clearance despite the possibilities of being unstable

And guns were banned on the installation. It didn't stop this guy.

So the guns magically teleported through DC? People on base aside from MP's are allowed firearms?

No and no.

Just because Elmo is a psychotic gun toting, federal judge murdering muppet holding a martini glass that looks like a pistol doesn't mean he's wrong.

Except he is. Lots of employees there had firearms. People were still shot.

Security had firearms. No one else did. Just like it is in the streets of Chicago and DC.

Are you suggesting that the densities of security between a secure military facility and the streets of Chicago are similar?