Woodward, Okla. — WASHINGTON (AP) — A former Navy reservist went on a shooting rampage Monday inside a building at the heavily secured Washington Navy Yard, firing from a balcony onto office workers in an atrium below, authorities and witnesses said. Thirteen people were killed, including the gunman.
Authorities 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.
Investigators said they had not established a motive for the attack, which unfolded about 8:20 a.m. in the heart of the nation's capital, less than four miles from the White House and two miles from the Capitol.
Mayor Vincent Gray said there was no indication it was a terrorist attack, but he added that the possibility had not been ruled out.
It was the deadliest shooting rampage at a U.S.-based military installation since Maj. Nidal Hasan killed 13 people and wounded more than 30 others in 2009 at Fort Hood in Texas. He was convicted last month and sentenced to death.
President Barack Obama lamented yet another mass shooting in the U.S. that he said took the lives of American patriots. He promised to make sure "whoever carried out this cowardly act is held responsible."
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.