Aaron Alexis
Authorities identified one of the two possible shooters as Aaron Alexis. One gunman was dead, and police hunted for a second possible attacker who may have been disguised in a military-style uniform, police said.
Investigators said they had not established a motive for the shooting rampage, which unfolded less than four miles from the White House. As for whether it may have been a terrorist attack, Mayor Vincent Gray said: "We don't have any reason to think that at this stage."
The FBI took charge of the investigation.
The area that was targeted, known as Building 197, was part of the headquarters for Naval Sea Systems Command, which buys, builds and maintains ships, submarines and combat systems. About 3,000 people work at the headquarters, many of them civilians.
Witnesses described a gunman opening fire from a fourth-floor overlook, aiming down on people in the first-floor cafeteria. Others said a gunman fired at them in a third-floor hallway. It was not clear whether the witnesses on different floors were describing the same gunman.
Todd Brundidge, an executive assistant with Navy Sea Systems Command, said he and other co-workers encountered a gunman in a long hallway on the third floor. The gunman was wearing all blue, he said.
"He just turned and started firing," Brundidge said.
Terrie Durham, an executive assistant with the same agency, said she also saw the gunman firing toward her and Brundidge.
"He aimed high and missed," she said. "He said nothing. As soon as I realized he was shooting, we just said, 'Get out of the building.'"
Rick Mason, a civilian program-management analyst for the Navy who works on the fourth floor of the building, said a gunman was firing from the overlook in the hallway outside his office.
Shortly after the gunfire, Mason said, someone on an overhead speaker told workers to seek shelter and later to head for the gates at the complex.
Patricia Ward, a logistics-management specialist, said she was in the cafeteria getting breakfast.
"It was three gunshots straight in a row — pop, pop, pop. Three seconds later, it was pop, pop, pop, pop, pop, so it was like about a total of seven gunshots, and we just started running," Ward said.
Ward said security officers started directing people out of the building with guns drawn.
One person died at George Washington University Hospital of a single gunshot wound to the left temple, said Dr. Babak Sarani, director of trauma and acute care surgery. A police officer and two civilian women were in critical condition at Washington Hospital Center, said Janis Orlowski, the hospital's chief operating officer.
Orlowski said the police officer was in the operating room with gunshot wounds to the legs. The police chief said the officer was wounded when he engaged the shooter who later died.
One woman at the hospital had a gunshot wound to the shoulder. The other had gunshot wounds to the head and hand.
Adm. Jonathan Greenert, chief of naval operations, was at the base at the time the shooting began but was moved unharmed to a nearby military installation.
Alexis was arrested in Fort Worth on September 5, 2010, for discharging a gun in the Fort Worth city limits. But Melody McDonald, spokesperson for the Tarrant County District Attorney, says he was never charged with a crime in Tarrant County.
She says finding more information about the case will take time: "We have to find out what kind of case it was, who it went to. But he never had a pending case in this office."
Alexis was released from Fort Worth city jail the same day he was arrested.
“He has never been charged with a crime in Tarrant County,” says McDonald, “at least not as an adult.”
In D.C. on Monday, security was beefed up at the Capitol and other federal buildings, but officials said there was no known threat.
President Barack Obama mourned yet another mass shooting in the U.S. that he said took the lives of American patriots. Obama promised to make sure "whoever carried out this cowardly act is held responsible."
Anxious relatives and friends of those who work at the Navy complex waited to hear from loved ones.
Tech Sgt. David Reyes, who works at Andrews Air Force Base, said he was waiting to pick up his wife, Dina, who was under lockdown in a building next to where the shooting happened. She sent him a text message about being on lockdown.
"They are under lockdown because they just don't know," Reyes said. "They have to check every building in there, and they have to check every room and just, of course, a lot of rooms and a lot of buildings."
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. Only security personnel were allowed to be armed on the grounds.
Mason, the program management analyst for the Navy, said there are multiple levels of security to reach his office. Everyone must show a building ID to get through a main gate, and at the building entrance, everyone must swipe a badge to pass through either a door or gate, depending on the entrance.
That “makes me think it might have been someone who works here,” he said.
The Navy Yard has three gates, according to its website. One is open around the clock and must be used by visitors. A second gate is only for military and civilian Defense Department employees. The third gate is for bus traffic.
The Navy Yard is part of a fast-growing neighborhood on the banks of the Anacostia River in southeast Washington, blocks from the Nationals Park baseball stadium.