D.C. Police Chief Cathy Lanier says authorities believe there was only a lone gunman responsible for the Navy Yard shooting rampage that left 13 people dead.
Authorities had earlier said they were searching for a possible second suspect.
Mayor Vincent Gray says the 12 shooting victims range in age from 46 to 73 years old. The gunman, identified as 34-year-old Aaron Alexis, was killed after a running gun battle inside the building with police.
Gray said at a news conference late Monday night that they are still notifying the families of about half of the 12 people who were killed.
The FBI says the gunman used a valid pass to get on to the Navy Yard.
Law enforcement officials say Aaron Alexis was carrying three weapons during the rampage. Two federal officials say he had an AR-15 assault rifle, a shotgun and a handgun that he took from a police officer at the scene.
Here are some biographical details on Alexis:
NAME: Aaron Alexis. AGE: 34 (born May 9, 1979). HOMETOWN: New York City. LAST RESIDENCE: Fort Worth, Texas.
OCCUPATION: Worked for The Experts, a subcontractor on an HP Enterprise Services contract to refresh equipment used on the Navy Marine Corps Intranet network. Navy reservist from 2007-2011; left as a petty officer 3rd class, stationed in Fort Worth. After discharge, worked as a waiter and delivery driver at the Happy Bowl Thai restaurant in White Settlement, a suburb of Fort Worth, until May 2013.
EDUCATION: Was pursuing a bachelor's degree in aeronautics via online classes at Embry-Riddle Aeronautical University.
RELIGION: Converted to Buddhism and was devout, wanting to become an ordained monk, according to friends.
ARREST RECORD: In September 2010, Alexis was arrested on suspicion of discharging a firearm within city limits after a neighbor reported she was nearly shot by a bullet fired from his downstairs apartment. He told police his gun accidentally discharged while he was cleaning it, and no charges were filed. In May 2004, he was arrested in Seattle for shooting out the tires of another man's vehicle in what he later described to detectives as an anger-fueled "blackout."
QUOTE: "I wouldn't call him nice, but he seemed harmless, if really awkward," said Gene Demby of Philadelphia, who said he dated one of Alexis' younger sisters in the early 2000s. "He was insecure. He was like a barbershop conspiracy theorist, the kind of guy who believes he's smarter than everyone else. He also was kind of like perpetually aggrieved, but not megalomaniacal or delusional."
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