WASHINGTON (AP) - A former Navy reservist went on a shooting rampage Monday inside a building at a heavily secured U.S. Navy complex, firing from a balcony onto office workers in an atrium below, authorities and witnesses said. Thirteen people were killed, including the gunman.
President Barack Obama lamented "yet another mass shooting" in the U.S. that he said took the lives of American "patriots" and promised to make sure "whoever carried out this cowardly act is held responsible." Despite a string of mass shootings, Obama has been powerless to get gun control legislation passed amid a fierce backlash from conservative politicians and the gun owners lobby.
The attack at the Washington Navy Yard was the deadliest shooting at a U.S.-based military installation since Maj. Nidal Hissan, an Army psychiatrist, killed 13 people and wounded 30 others in 2009 at Fort Hood in Texas. He was convicted last month and sentenced to death.
Authorities earlier said they were looking for a possible second attacker who may have been disguised in an olive-drab military-style uniform. But as the day wore on and night fell, the rampage increasingly appeared to be the work of a lone gunman.
The attack unfolded about 8:20 a.m. in the heart of the U.S. capital, less than four miles (6.5 kilometers) from the White House and two miles (3.2 kilometers) from the Capitol.
Investigators said the motive was a mystery.
Mayor Vincent Gray said there was no indication it was a terrorist attack. But he said the possibility had not been ruled out.
The FBI took charge of the investigation and identified the gunman killed in the attack as 34-year-old Aaron Alexis of Texas. He died after a running gunbattle inside the building with police, investigators said.
At the time of the rampage, Alexis was working in information technology with a company that was a Defense Department subcontractor.
Authorities said he may have had a badge that enabled him to get onto the base, but they were still investigating.
Alexis was 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.
Alexis had had run-ins with the law over shooting incidents in 2004 and 2010 in Fort Worth, Texas, 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.
In addition to those killed, more than a dozen people were hurt, including a police officer and two female civilians who were shot and wounded. They were all expected to survive.
Police would not give any details on the gunman's weaponry, but witnesses said the man they saw had a long gun -- which can mean a rifle or a shotgun.
The shooting quickly reignited the debate over gun control in the United States, but it was far from certain what the impact would be.
The politics of gun control have only gotten tougher since December's shooting at Connecticut's Sandy Hook Elementary School. That shooting, which killed 20 first-graders and six staffers, spurred Obama to propose stricter firearms laws.
White House spokesman Jay Carney on Monday reiterated the Obama administration's commitment to strengthening gun laws, including expanding background checks to sales online and at gun shows.
Gun owners, aided by their advocates at the National Rifle Association, the country's largest gun rights lobby, have successfully fought Obama's legislation, even though polls show broad support for tougher gun laws.
The Washington Navy Yard is a sprawling, 41-acre (16.6-hectare) 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.
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."'
As emergency vehicles and law enforcement