Aaron Alexis began Navy Yard shooting with shotgun, then obtained pistol

REPORTING FROM WASHINGTON —  Aaron Alexis, the gunman at the historic Washington Navy Yard, entered the base armed with only a shotgun then apparently “gained access” to a handgun after he began shooting, eventually killing 12 people, the FBI agent in charge of the investigation said Tuesday.

In addition, Washington’s police chief described how officers arrived at the scene within minutes, found the building where Alexis was killing and wounding co-workers and exchanged gunfire with him for “at least 30 minutes” before fatally shooting the 34-year-old gunman and bringing the rampage to a stop.

The disclosures by the two top law enforcement officials in the case began to give a clearer picture of the moments after 8:15 a.m. Monday when Alexis, a Navy contractor and former member Navy enlisted man from Fort Worth, entered the base, which is located along Washington’s Anacostia River waterfront.

FULL COVERAGE: Navy Yard shooting

Valerie Parlave, assistant director in charge of the FBI’s Washington field office, said Alexis arrived in Washington around Aug. 25 and began staying in “local hotels,” including a Residence Inn near the base that he moved into on Sept. 7. He had worked at bases in several cities in recent months as part of his job helping to maintain computer systems.

Alexis reported to the base Monday morning, Parlave said, noting that he “had legitimate access to the Navy Yard as a result of his work as a contractor, and he utilized a valid pass to gain entry to the building.” He was carrying with him the shotgun, which he had recently legally purchased from a gun store in a Virginia suburb.

Officials have said the shotgun was purchased from Sharp Shooters in Lorton, Va. The owner of the store refused to comment and directed questions to his attorney. The attorney, J. Michael Slocum, said his firm will respond with a written statement after it first is “reviewed and approved” by federal law enforcement officials.

“Once inside the facility, and after he began shooting,” Alexis “may have gained access to a handgun,” Parlave said. Investigators believe he took a weapon from a base security guard whom he shot. Contrary to previous reports that had been widely circulated, Parlave said Alexis did not use an AR-15 semiautomatic weapon.

Cathy Lanier, chief of Washington’s Metro Police Department, said police officers were at the Navy Yard within two minutes of the first calls for help. Within four or five minutes, she said, seven police units were going through the gates and trying to determine where the gunfire was coming from.

“There were different buildings, different calls and different building numbers,” she said. After some minutes passed, “we had units outside the building where the shooter was, and they could hear another round of gunfire. They entered immediately, and two of them started giving lookouts and passing information along,” Lanier said.

PHOTOS: At the scene of Navy Yard shooting

“There were multiple engagements with the suspect with multiple agencies before the final shots were fired,” she said. In addition to the D.C. police, units from the Park Police, Navy security, the FBI and other agencies were involved. Lanier estimated that the gunfight lasted at least a half hour, but “not more than an hour.”

Lanier said that once the officers engaged Alexis in the gun battle, “there is no doubt in my mind they saved numerous lives.”

“It was a horrible tragedy,” she added. “We hope it never happens again anywhere.”

Parlave said the FBI believes that Alexis “acted alone.” But Ronald C. Machen Jr., the U.S. attorney in Washington, said federal prosecutors are still investigating to see if others had assisted him in any way, even unknowingly.

“We’re not going to stop until we get answers to these questions,” he said.

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richard.serrano@latimes.com