A gunman who died after killing 12 people at a naval installation in Washington has been identified as a former navy reservist.
Aaron Alexis, 34, was killed in a gunbattle with police during the rampage at Washington Navy Yard on September 16.
Eight people were also wounded in the shooting.
Valerie Parlave, assistant director of the FBI's Washington field office, told reporters that the shooter was from Fort Worth, Texas. She also made a public appeal for more information on him.
"We have posted photographs of Mr. Alexis on our website, Fbi.gov, and we ask anyone with information about him to contact us," she said.
Police initially searched for two other possible armed suspects but later said Alexis was the only attacker.
Witnesses said Alexis sprayed bullets at workers in a cafeteria and in a hallway.
A motive has not yet been determined.
At the time of the shooting, Alexis worked for the Experts, a subcontractor hired to refresh equipment used on the Navy Marine Corps Intranet network.
The FBI said he had a valid pass, giving him access to the Washington Navy Yard.
The U.S. Navy said the suspect was formerly a petty officer 3rd class who served full-time in the naval reserve between 2007 and 2011.
Reports say he was a Buddhist convert who had previous gun-related brushes with the law.
At the White House, President Barack Obama said he mourned "yet another mass shooting" and condemned what he called a "cowardly act."
"It's a shooting that targeted our military and civilian personnel," he said. "These are men and women who were going to work and doing their job, protecting all of us."
"They know the dangers of serving abroad, but today they face the unimaginable violence that they wouldn't have expected here at home."
Obama ordered flags on federal property to be flown at half-staff through September 20.
The White House also decided to postpone the taping of a program, scheduled for September 16, celebrating Latin music. And a professional baseball game at the Washington Nationals stadium was called off.
The Naval Sea Systems Command, which employs some 3,000 people, builds and purchases U.S. warships and combat systems.
It is the oldest shore facility of the U.S. Navy.
Washington Navy Base Gunman Identified
A police helicopter patroling over the Washington Navy Yard on September 16.