Aaron Alexis, the alleged Washington Navy Yard shooter, entered the facility carrying a legally-purchased shotgun Monday morning and proceeded to kill 12 people and wound 8 others, law enforcement officials said Tuesday.
The now deceased suspect – who was killed in a gunfight with police – may have also obtained a handgun from one of his victims inside the building, where a mix of civilians and military personnel worked.
Valerie Parlave, assistant director in charge of the FBI Washington field office, also put to rest news reports that Alexis used an AR-15 – a military-style assault weapon – as part of his rampage. That gun gained notoriety following its use by Adam Lanza in the Newtown, Conn. elementary school massacre.
"At this time we believe that Mr. Alexis entered Building 197 at the Navy Yard with a shotgun; we do not have any information at this time that he had an AR-15 in his possession," she said during an afternoon news briefing. "We also believe Mr. Alexis may have gained access to a handgun once inside the facility and after he began shooting."
The former Navy reservist, who was honorably discharged in 2011, had valid access to the building because of his work as a defense contractor, Parlave said.
In the wake of the attack, Defense Secretary Chuck Hagel has ordered a worldwide security review of all military installations. And according to a report by Time Magazine, a yet-to-be-released Department of Defense Inspector General report faults the Navy for cutting corners to save money but "did not effectively mitigate access-control risks associated with contractor-installation access." That revelation could come in to play politically as Congress and the White House gear up to make a deal on government funding levels.
Law enforcement officials would not address questions about the report during Tuesday's press briefing.
"We continue to conduct interviews, exploit digital media and run down every lead we can to piece together his recent movements and determine the motive behind his attack," Parlave said of the FBI's on-going investigation. "We can say that we have determined Mr. Alexis arrived in the Washington, D.C. area on or about Aug. 25 and he has stayed at local hotels in the area since that time."
But officials remained tight-lipped about Alexis' potential motive.
"So the motivation, whatever that motivation is, is currently under investigation, I'm not going to comment on that," Parlave said.
D.C. Police Chief Cathy Lanier defended her decision to keep the neighboring area around the Navy Yard in southeast Washington under a "shelter in place" order until 10 p.m. Monday as police searched for a lingering person of interest.
"We had information that we could not dismiss so we thought that was the most prudent decision at the time," she said. "I think it was the right decision."
Lanier also reiterated her praise for the way law enforcement officials from different agencies came together to neutralize the situation and prevent more carnage.
"We had officers who heroically went into a building, witnessing multiple tragedies and continued to pursue and engage a gunman who was determined to kill as many people as possible," she said. "The more we look into this, the officers that responded from all of the agencies did an incredible job and there's no doubt in my mind that they saved numerous lives."
Police identified the deceased in a series of press conferences starting late Monday and early Tuesday. The 12 victims are: Michael Arnold, 59; Martin Bodrog, 54; Arthur Daniels, 51; Sylvia Frasier, 53; Kathy Gaarde, 62; John Roger Johnson, 73; Mary Francis Knight, 51; Frank Kohler, 50; Vishnu Shalchendia Pandit, 61; Kenneth Bernard Proctor, 46; Gerald L. Read, 58; and Richard Michael Ridgell, 52.
Parlave said teams of forensic teams are continuing to examine and process the crime scene.
"Our evidence response teams remain at the Navy Yard and continue to process the scenes," she said. "This is a methodical and time-intensive process that includes bullet trajectory and crime scene mapping."