Authorities in Washington, D.C. say an information technology employee working for a military contractor was the lone suspect in Monday's shooting rampage at a U.S. naval facility that left 13 people dead, including the gunman.
Washington Police Chief Cathy Lanier told reporters hours after the tragedy there was no evidence a second person was involved with Aaron Alexis, a 34-year-old resident of Fort Worth, Texas, who was killed during a gun battle with police shortly after his shooting spree began.
Police say Alexis entered the U.S. Naval Yard in the nation's capital with a valid identification card, and was armed with at least one firearm. He then opened fire inside the Naval Sea Systems Command, which is responsible for buying, building and maintaining ships and submarines. About 3,000 people work in the building, many of them civilians.
The New York City native served in the U.S. Navy as a reserve sailor from 2007 to 2011. News outlets say Alexis was arrested in two separate shooting incidents, with one taking place in 2004 in Seattle and a second in Fort Worth in 2010. He has been described as having problems controlling his anger.
Washington Mayor Vincent Gray said that eight people were hurt in addition to the dead in Monday's incident. All the injured are expected to survive. Mr. Gray said there was no apparent motive behind the shooting.
Police released the identities of those killed late Monday night, with their ages ranging from the late 40s to the early 70s.
Related video report by Chris Simkins
As night fell in the nation's capital, grieving residents gathered outside the Naval Yard and held a silent candlelight vigil. The complex is in a residential area close to the U.S. Capitol. People in the neighborhood had been ordered to stay in their homes and offices as police searched earlier for a possible second gunman. A number of schools and U.S. Senate offices were locked down during the day Monday.
Monday night's baseball game between the Atlanta Braves and the host Washington Nationals at a nearby stadium also was canceled.
U.S. President Barack Obama has ordered all flags across the country to fly at half-staff through sunset Friday to honor the victims. During an event at the White House Monday, Obama lamented yet another mass shooting, which he called a "cowardly act.''