Navy officials identified Aaron Alexis as the suspected gunman who killed a dozen people at the Washington Navy Yard Monday morning before he was shot dead.

Officials are still unsure what may have triggered the 34-year-old Navy veteran to go off on a shooting spree, however, this apparently isn't the first time Alexis was reported for foul behavior with a firearm.

Alexis grew up in Brooklyn with his parents, Cathleen and Anthony Alexis, and lived in Texas, New York and Washington State in recent years, reports The Washington Post. He spent nearly four years in the Navy as a full-time reservist from May 2007 until January 2011 before he received a general discharge for "misconduct" due to two events involving a firearm.

The first incident occurred in 2004 when he was arrested in Seattle for firing three shots from a Glock pistol into the tires of a Honda Accord that two construction workers had parked in a driveway adjacent to Alexis' house. Alexis justified his behavior by claiming the construction workers had "mocked" and "disrespected" him and said that he had had "a black-out fueled by anger."

At the time, Alexis' father told detectives that his son "had experienced anger management problems that the family believed was associated with PTSD," or Post-Traumatic Stress Disorder, according to the police report. His father said that Alexis "was an active participant in rescue attempts of Sept. 11, 2001," reports USA Today.

Alexis was involved in another confrontation while he was living in gated townhouse community in Fort Worth, Texas. In September 2010, police were called to his apartment after his downstairs neighbor complained that he had fired a bullet through his floor and through her ceiling.

The woman told cops that she had called several times about Alexis being too loud, but that nothing had been done. She said he had confronted her a few days earlier in the complex's parking lot, where he complained that she had been making too much noise. The woman said that she was "terrified of Aaron and feels that this was done intentionally," the police report said. Alexis told police that he had been cleaning his gun while he was cooking. He said that he accidentally discharged the weapon because his hands were greasy, according to the police report.

Alexis was arrested in connection with improper discharge of a firearm, but the county district attorney's office said Monday that there was not enough evidence to pursue the case, so no charges were brought. A couple of weeks later, the apartment complex began eviction proceedings against Alexis, according to county court records.

About four months ago, Alexis headed to Washington where he had been working as an hourly tech employee for the Experts, a Hewlett-Packard subcontractor that is updating computer systems at Navy and Marine Corps installations worldwide.

Those who knew Alexis in recent years describe him as a "sweet and intelligent guy" (a regular customer at the Thai restaurant where he had been a waiter) and "a good boy" (his landlord), but also as "very aggressive," someone who seemed as though he might one day kill himself (a lay worker at the Buddhist temple where Alexis worshiped).

He also lived for a time in a bungalow in the woods near a Buddhist temple in Fort Worth, where he occasionally joined Thai immigrants in meditation.

A former employer described the alleged shooter as an immature person who liked to drink and play video games. Oui Suthamtewakul, owner of The Happy Bowl, a Thai restaurant where Aaron Alexis worked in Fort Worth, added that he always carried his gun and was suspicious of American women, reports The Post.

"He can start drinking at 9:30 in the morning," Suthamteakul said, adding that, "He's not an alcoholic, he just drinks a lot."

Alexis also carried a gun "at all times," he recalled - specifically, a .45-caliber handgun that Alexis would keep with him at the restaurant.

Suthamteakul said he was "shocked" to learn the news on Monday. "When I heard the news today - that's just not him," he said. "I can't believe he did that - if he did that," he added.

Officials at the university confirmed that Alexis was enrolled "as a worldwide online student via our Fort Worth campus. He started classes in July 2012 and was pursuing a bachelor's of science in aeronautics."