Valerie Parlave, head of the FBI’s field office in Washington, said Alexis had access to the Navy Yard as a defense contractor and used a valid pass.
Alexis had been a full-time Navy reservist from 2007 to early 2011, leaving as a petty officer third class, the Navy said. It did not say why he left. He had been an aviation electrician’s mate with a unit in Fort Worth.
A convert to Buddhism who grew up in New York City, Alexis had had run-ins with the law over shooting incidents in 2004 and 2010 in Fort Worth and Seattle and was portrayed in police reports as seething with anger.
The Washington Navy Yard is a sprawling, 41-acre labyrinth of buildings and streets protected by armed guards and metal detectors, and employees have to show their IDs at doors and gates. More than 18,000 people work there.
The rampage took place at Building 197, the headquarters for Naval Sea Systems Command, which buys, builds and maintains ships and submarines. About 3,000 people work at headquarters, many of them civilians.
Witnesses on Monday described a gunman opening fire from a fourth-floor overlook, aiming down on people on the main floor, which includes a glass-walled cafeteria. Others said a gunman fired at them in a third-floor hallway.
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.
Todd Brundidge, an executive assistant with Navy Sea Systems Command, said he and 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 the gunman fired 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.’”
Officials announced early Tuesday that streets around the Navy Yard that were closed after the shooting were re-opened for the morning commute.
As emergency vehicles and law enforcement officers flooded the streets Monday, a helicopter hovered, nearby schools were locked down and airplanes at Reagan National Airport were grounded so they would not interfere with law-enforcement choppers.
In the confusion, police said around midday that they were searching for two accomplices 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. Police said it was unclear if the men were members of the military.
But as the day wore, police dropped one person and then the other as suspects. As tensions eased, Navy Yard employees were gradually released from the complex, and children were let out of their locked-down schools.
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.
Anxious relatives and friends of those who work at the complex waited to hear from loved ones.