At least one gunman was dead Monday morning and as many as two others are being sought by police after a rampage at a naval facility in the nation's capital that left almost a dozen people dead or injured, according D.C. police.
The first reports of the violence came in at 8:20 a.m. as the nation's capital was heading to work, prompting fears of a terrorist attack, but it was too early to determine the motivation behind the violence.
D.C. Police Chief Cathy Lanier said that multiple people had been killed and others had been wounded including a police officer. He is in stable condition at an area hospital.
"We potentially have two other shooters that we have not located at this point," she said.
One was white male, last seen in a khaki tan military uniform, wearing a beret and carrying a handgun. The other was a black male about 50 years old in an olive drab colored military style uniform and with a rifle.
"We do have information that those individuals are wearing military style uniforms," Lanier said, but added that there was no evidence to confirm whether they were actually military personnel. She asked the public for help in locating them.
Multiple news reports said that at least 11 people had been killed or injured by the gunmen in the military installation near Capitol Hill. The area around the naval building had been sealed off by layers of law enforcement personnel from local and federal agencies.
President Obama vowed that his administration would do "everything in our power to make sure whoever carried out this cowardly act is held responsible."
"So we're confronting yet another mass shooting, and today it happened on a military installation in our nation's capital. It's a shooting that targeted our military and civilian personnel. These were men and women who were going to work, doing their job, protecting all of us. They're patriots. And they know the dangers of serving abroad, but today, they faced the unimaginable violence that they wouldn't have expected here at home."
The president ordered his aides to ensure that the investigation is "seamless, so that federal and local authorities are working together."
The shooting began inside the Naval Sea Systems Command Headquarters building, a workplace for 3,000 people, according to a press release from Naval District Washington.
Patricia Ward, a logistics management specialist, told gathered reporters that she was near the cafeteria area when she heard some shots, followed by a break and then more shots. She and others fled the building; someone pulled a fire alarm to alert colleagues of a problem.
Eleven victims were confirmed, said a District of Columbia police department spokesman said. Of the 11, one is a navy procurement directive officer and another is a base officer, said a spokeswoman for the police department, who did not clarify if the two were dead or injured.
Helicopters circled overhead for much of the morning and a variety of police and rescue vehicles choked off the area in a scene eerily similar to Hollywood thrillers. The huge police presence prompted fears that terrorism was possibly involved, but there was no evidence confirming or negating that fear.
Witnesses described one gunman dressed in dark clothing with what appeared to be a double-barreled shotgun, perched on a mezzanine and firing at a cafeteria atrium below.
A hospital doctor said arriving victims described hearing the rapid-fire shots of an automatic or semiautomatic rifle.
Three victims were brought to MedStar Washington Hospital Center, and the center is expecting more to arrive. In a press conference, Chief Medical Officer Janis Orlowski said the chances of their survival are "good." She also confirmed that all three victims were alert and speaking.
One of the patients is a police officer who was shot in both of his lower extremities. The other two are both female civilians. One sustained injuries to her shoulder, the other to both her head and her hand; she is on her way to surgery. All three are confirmed to have been wounded inside the Navy Yard.
Orlowski was not aware of any victims taken to other hospitals, but said all hospitals in the area were standing by prepared. She said there have been reported victims who will not be transported because they died at the scene, but the exact number is unknown.
MedStar Washington Center has partnered with the Children's Hospital and the V.A. Hospital to create a tighter perimeter and heightened security on the campus. The hospital is "standing by to receive anyone else who is transported [there]."
An elite team from the Bureau of Alcohol, Tobacco, Firearms and Explosives was dispatched to the scene Monday. It was part of the same ATF Special Response Team Canine Program that helped capture the alleged Boston Marathon bomber.
Employees at the headquarters are comprised of civilians, service members and contract support personnel. They are responsible for engineering, building, purchasing and maintaining naval ships, submarines and combat systems. The Naval Sea Systems Command is the largest of the branch's five systems commands.
This is not the first shooting at a military installation in recent years. In 2009 at Fort Hood, Texas, Army psychiatrist, Maj. Nidal Malik Hasan, 39 at the time, killed 12 and wounded 31 service members. Another, less known incident occurred on June 10, 2013, at Fort Sam Houston in San Antonio where a soldier shot and wounded a fellow service member.
As word spread of a shooting at the Navy Yard, the end of the D.C. morning rush hour began to look like the crush of peak hour. At least two bridges into the nation's capital were closed to traffic and commuters were forced to inch along the side roads to get in or turn back and work from home.
Subway service was briefly interrupted and there was no additional policing that was apparent to the untrained eye. That argued in favor of a localized incident that didn't spark fears of a wider terror plot.
There were subtle signs security was tighter Monday on Capitol Hill. Two armed policemen stood just outside Union Station, about five blocks from the Capitol. Normally there is no such obvious security.
In those five blocks that lead to the Capitol, there is in fact lots of daily security – checkpoints cars must pass through, armed policemen at each intersection, policemen on bicycles patrolling the parks.
David Lightman, Greg Gordon, Marisa Taylor, Mary Faddoul and Kendall Helblig, Tish Wells and William Douglas contributed to this report.
By Kevin G. Hall
McClatchy Washington Bureau