The FBI took charge of the investigation.
At the time of the rampage, Alexis was an information technology employee with a company that was a Defense Department subcontractor, authorities said. Valerie Parlave, head of the FBI’s field office in Washington, said he had access to the base as a defense contractor.
The dead ranged in age from 46 to 73, according to the mayor. A number of the victims were civilian employees and contractors, rather than active-duty military personnel, the police chief said.
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, Texas.
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.
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.