Aaron Alexis, the 34-year-old man believed responsible for Monday's shooting rampage that killed 12 people at the Washington Navy Yard, was a former full-time Navy reservist who had obtained a concealed-carry permit in Texas and was arrested three years ago for illegally discharging a weapon.
Witnesses at the scene of Monday's carnage at the Navy Yard described "a sense of panic."
Alexis, who was also killed on Monday, was an aviation electrician's mate third class in the U.S. Navy Reserve until January 2011, when he received a general discharge amid unspecified "misconduct issues," a Navy official tells NPR.
He was last attached to Fleet Logistics Support Squadron 46 in Fort Worth, Texas. A biography supplied by the Pentagon said he was originally from New York City.
The Navy says Alexis had been awarded the National Defense Service Medal and the Global War on Terrorism Service Medal.
Authorities say that so far they have no motive for the attack.
Valerie Parlave, the assistant director of the FBI's Washington field office, has urged the public to come forward with information regarding Alexis. "No piece of information is too small," she was quoted by The New York Times as saying. "We are looking to learn everything we can about his recent movements, his contacts and his associates."
The Times says three weapons -- an AR-15-style assault rifle, a shotgun and a semi-automatic pistol, were found on the gunman.
The Fort Worth Star-Telegram quoted Nutpisit Suthamtewakul, owner of the Happy Bowl Thai in White Settlement, Texas, who said he'd lived with Alexis for three years.
Suthamtewakul described Alexis as "my best friend" and was shocked to learn he'd been killed.
"I don't think he'd do this. He has a gun, but I don't think he's that stupid. He didn't seem aggressive to me," he told the newspaper.
The Star-Telegram said a police report filed in September 2010 detailed his arrest for discharging a firearm within a municipality:
"Police were dispatched to the Oak Hills apartments about 6:40 p.m. Sept 4, 2010, on a report that someone had fired a shot through the floor and into the ceiling of a woman's apartment, according to a Fort Worth police report.
"The woman told police she had been sitting in a chair when she heard a loud pop and saw dust.
"'She then saw that there was a hole in her floor just a couple of feet from where she was sitting while shredding papers and a hole in the ceiling,' the report states. 'She told me that she believed someone had shot a bullet through her apartment.'
"The woman told police that Alexis, her downstairs neighbor, did not come up to check on her after the shooting.
"She said that Alexis had called police on her several times in the past for 'being loud' but that police never heard anything and therefore, no action was taken.
"'She said that several days ago Aaron confronted her in the parking lot about making too much noise,' the report states.
"The woman told police that she was 'terrified' of Alexis and felt the shooting was done intentionally."
According to the Seattle Police Department Blotter:
"Alexis also told police he was present during 'the tragic events of September 11, 2001' and described 'how those events had disturbed him.'
"Detectives later spoke with Alexis' father, who lived in New York at the time, who told police Alexis had anger management problems associated with PTSD, and that Alexis had been an active participant in rescue attempts on September 11th, 2001."
