People evacuate a building after a shooting at the Washington Navy Yard.… (Alex Wong / Getty Images )
WASHINGTON — A gunman who had been discharged by the Navy in 2011 after what an official described as a "pattern of misconduct" staged a two-hour rampage Monday at the Washington Navy Yard, killing 12 people before being shot to death by law enforcement officials.
Officials using fingerprint records identified the man as Aaron Alexis, 34, a Navy contractor, whose arrival on the base shortly before 8:15 a.m. set off hours of terror and mayhem.
More than 3,000 workers were locked down in their offices while police officers, Navy security guards and FBI agents fought a running gun battle with the shooter, who was armed with an AR-15 assault rifle, a shotgun and a handgun. Investigators think Alexis began the assault with only the shotgun and that he took the AR-15 and handgun from people he shot, a U.S. official said.
Officials said Alexis got to the fourth floor of the headquarters building of the Naval Sea Systems Command and started shooting down into an atrium that includes an employee cafeteria.
"I heard pop, pop, pop and then maybe three seconds later, four more shots," said Patricia Ward, who was in the building when the shooting started.
The 53-year-old logistics management specialist in the Sea Systems Command was in the lobby using an ATM when she heard the shots. A security guard with a gun drawn told workers to run, she said.
"I thought of my family and I just ran," Ward said.
The dead ranged in age from 46 to 73, Washington Mayor Vincent Gray said at a late-night news conference. Officials have begun notifying families of the dead but have not released their names. All were civilian Navy employees or contractors.
Officials said they had no indication the incident was linked to terrorist groups but had no certainty about what the motive might have been.
An official close to the investigation, however, said federal authorities were looking into the possibility that Alexis had a dispute with his employer, a company called The Experts, which works as a subcontractor to a division of Hewlett-Packard.
The official said Alexis was "particularly upset over a pay or salary dispute" from work he had performed in Asia for the company. Alexis believed the company had shorted him on his wages for work he had performed in Japan, the official said.
Howard Clabo, Hewlett-Packard senior vice president for global communications, said the company was cooperating with the investigation. A spokesman for The Experts said the firm also was cooperating.
The FBI appealed for the public's help to learn about Alexis.
"No piece of information is too small," Valerie Parlave, assistant director in charge of the FBI's Washington field office, said at a news conference. "We are looking to learn everything we can about his recent movements, his contacts and his associates."
Alexis, a New York City native who had recently moved to Washington from Fort Worth, had a record that included at least two arrests in the last decade involving firearms, but neither seemed to presage violence on the scale of Monday's attacks.
One of the previous incidents occurred in 2010 in Fort Worth, when Alexis shot through the ceiling of his apartment. Tarrant County prosecutors said Monday they had not prosecuted the case after Alexis told them the gun had discharged accidentally while he was cleaning it.
In the other case, Seattle police arrested Alexis in 2004 after he purportedly shot out the tires of another man's vehicle in what he later described to detectives as an anger-fueled "blackout." Detectives spoke with Alexis' father, who, according to the police department blog, told police Alexis had "anger management problems."
A Navy official said that Alexis, who had served for four years as an aviation electrician's mate, had multiple disciplinary infractions before his discharge in January 2011. But the incidents were not serious enough to prevent him from getting a job as an information technology worker on a Navy contract that involved equipment used by the Marine Corps Intranet network.
Parlave of the FBI said Alexis' job as a contractor gave him "legitimate access" to the base and that he had used a valid pass to enter. Military personnel and contractors can access the grounds without being searched if they have a valid pass, Navy officials said.
A federal law enforcement supervisor briefed on the investigation said an official Navy employee ID card was found near the scene of the shooting but that it apparently did not belong to Alexis. Instead, officials said it belonged to a different person who had been "let go or transferred" from his job recently.
Whether Alexis used that card and how he may have obtained it remained under investigation, officials said.