WASHINGTON — Navy Yard gunman Aaron Alexis cleared a security checkpoint with his contractor ID and carried his shotgun, unassembled, into Building 197 within minutes of starting his bloody rampage Monday, federal investigators said Tuesday.
Investigators revised and refined the details of events at the Naval Sea Systems Command headquarters that left 13 people dead, including Alexis, who was shot to death in a showdown with police.
A federal law enforcement official said Tuesday that Alexis, a former Navy reservist, had sought assistance from the Department of Veterans Affairs for mental illness as recently as a month ago. The official said the 34-year-old contractor recently paid about $540 to buy a 12-gauge shotgun and ammunition at a gun store in Virginia.
Contrary to earlier reports provided by law enforcement officials, Alexis was not believed to be in possession of an AR-15 assault rifle.
Valerie Parlave, chief of the FBI's Washington, D.C., field division, confirmed that Alexis was armed only with a shotgun when he arrived at the Navy Yard. Parlave said he obtained a handgun at some point during the attack.
"At this time, we believe that Mr. Alexis entered Building 197 at the Navy Yard with a shotgun," she said. "We do not have any information at this time that he had an AR-15 in his possession."
After Alexis fired several rounds randomly on the people below, the official said, he ran down a flight of stairs where he confronted and shot a security officer.
Investigators believe Alexis took the officer's handgun and returned to the overlook, where he continued to shoot. At some point, the official said, Alexis left that location, shot a victim described as a maintenance person or building staffer. He returned one last time to the overlook, where he was ultimately killed in a confrontation with police.
Metropolitan Police Chief Cathy Lanier said the first Washington police officers, two units, arrived on the scene two minutes after being dispatched.
Four minutes after the call, five to seven units had gone through the Navy Yard gates, she said. Seven minutes after the first dispatch call, two police units outside Building 197 heard shots fired and immediately entered the building, she said.
Lanier said she did not have the exact time of the final shootout that resulted in Alexis' death, but she said law enforcement officers from various agencies exchanged fire with Alexis several times. She said the entire incident lasted 30 to 60 minutes.
The federal official said investigators are just beginning to analyze Alexis' possessions to determine if they might reveal any motive for the slayings.
"It didn't appear that he had any plan for escape,'' the official said. "No one believes he was looking for anybody in particular," he said.
A witness, Rick Mason, a program management analyst, said the gunman was aiming down at people in the building's cafeteria on the first floor.
The Metropolitan Police Department identified the last of the victims Tuesday morning: Arthur Daniels, 51; Mary Francis Knight, 51; Gerald L. Read, 58; Martin Bodrog, 54; and Richard Michael Ridgell, 52.
The seven victims identified Monday night are Michael Arnold, 59; Sylvia Frasier, 53; Kathy Gaarde, 62; John Roger Johnson, 73; Frank Kohler, 50; Kenneth Bernard Proctor, 46; and Vishnu Pandit, 61.
All were civilian employees and contractors, officials said.
At least three people, including a city police officer, suffered non-fatal gunshot wounds inside Building 197. Hospital officials said all three were expected to recover. Authorities said five other people suffered minor non-gun injuries.
One of three victims hospitalized with gunshot wounds, a woman who suffered wounds to the head and hand, was discharged from MedStar Washington Hospital Center. Two others, including the officer, remain hospitalized in fair condition, the hospital said.
FBI Assistant Director Valerie Parlave declared Tuesday that law enforcement officials, who had worried on Monday that a second shooter might have been involved, now believe that Alexis "acted alone."
In another development, Defense Secretary Chuck Hagel called for a security review at military installations around the world in the wake of the shootings, a Pentagon official said Tuesday. The review will consider physical security and access to military bases.
It followed a call by Navy Secretary Ray Mabus for a review of security procedures at Navy and Marine bases. It is to be completed by Oct. 1.
"Our sailors, Marines, and civilians are familiar with the dangers of service, but our security is something we can never take for granted," Mabus said in a statement. "I ordered a review of every Navy and Marine Corps base in the United States to ensure that we live up to our responsibility of taking care of our people. "
Adm. William Gortney, commander of the U.S. Fleet Forces Command, will lead the review for the Navy. Lt. Gen. Rick Tryon, commander of the U.S. Marine Corps Forces Command, will lead the review for the Marine Corps.
Hagel and other officials did not offer any comments as they laid a wreath in honor of the victims, but the setting and the somber mood said it all.
As a servicemember played taps, Hagel, along with Chairman of the Joint Chiefs Martin Dempsey and Washington Mayor Vincent Gray, placed the wreath next to "The Lone Sailor" statue at the Navy Memorial that represents "all people who have ever served, are serving now, or are yet to serve in the United States Navy."