The killer behind Monday's rampage at the Washington Navy Yard acted alone and entered the facility with just one weapon, the FBI confirmed Tuesday afternoon.
Law enforcement officials also said Aaron Alexis, the 34-year-old discharged Navy engineer who claimed a dozen lives in a brutal massacre that shook the nation's capital, only came to Washington about three weeks ago.
"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," said Valerie Parlave, assistant director in charge at the FBI's Washington field office.
Ms. Parlave also confirmed that the shooter entered the Navy Yard Building 197 armed with just a shotgun.
"We do not have any information at this time that he had an AR-15 in his possession," she said. She added that it appears he may have picked up handguns once inside the building.
The shotgun used was bought legally at a Virginia shop, authorities said.
On the many other outstanding questions surrounding the shooting, Mr. Alexis' frame of mind and other aspects of the tragedy, officials largely were mum.
"As we have moved from a crisis stage to the investigation stage of this case, our focus and efforts are going to be on the questions we all have: What caused this individual to kill so many innocent men and woman? How did he carry out and plan this attack? How did he get access to the weapons? What could've been done to prevent this tragedy? And most importantly, whether anybody else aided him?" said Ronald Machen, U.S. attorney for D.C.
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