WASHINGTON — As many as two gunmen launched an attack Monday morning inside the Washington Navy Yard, spraying gunfire on office workers in the cafeteria and in the hallways at the heavily secured military installation in the heart of the nation's capital, authorities said. At least 13 people were killed, including one gunman, D.C. Mayor Vincent Gray said at a news conference.
The gunman died after he fired on a police officer, and police hunted for a second possible attacker who may have been disguised in a military-style uniform, authorities said. It wasn't clear how the gunman died.
In addition to the dead, at least three people were wounded. One of the injured included a D.C. police officer. A hospital official has said that the three people wounded are expected to survive.
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, Gray said: "We don't have any reason to think that at this stage."
The FBI took charge of the investigation. The dead gunman was identified as Aaron Alexis by two federal law enforcement officials who spoke on condition of anonymity because they were not authorized to speak publicly.
One of those officials said Alexis, 34, was from Texas and is believed to have gotten into the Navy Yard by using an employee's identification card. It is not yet clear if that person was an accomplice or if the ID was stolen.
In a statement, the Navy said Alexis was a full-time reservist from 2007 to 2011. He left the Navy on Jan. 31, 2011, as a petty officer 3rd class, according to the statement. It's not immediately clear why he left.
Alexis had been working for the fleet logistics support squadron No. 46, in Fort Worth, Texas. The Navy says his home of record was New York City.
Around midday, police said they were searching for two men who may have taken part in the attack — one carrying a handgun and wearing a tan Navy-style uniform and a beret, the other armed with a long gun and wearing an olive-green uniform. Washington Police Chief Cathy Lanier said it was unclear if those men were members of the military.
But later in the day, police said in a tweet that the man in the tan uniform had been identified and was not involved in the shooting.
As emergency vehicles and law enforcement officers flooded streets around the complex, a helicopter hovered overhead, nearby schools were locked down and airplanes at nearby Reagan National Airport were grounded so they would not interfere with law-enforcement choppers.
A short distance away, security was increased 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."
The area where the rampage took place, known as Building 197, was part of the headquarters for Naval Sea Systems Command, which buys, builds and maintains ships, submarines and combat systems. The yard is a labyrinth of buildings protected by armed guards at gates and metal detectors, and employees have to show their IDs to come and go.
About 3,000 people work at the headquarters, many of them civilians.
Read more in Tuesday's Arkansas Democrat-Gazette.