The Navy Yard gunman who killed 12 people Monday at a military facility in Washington typically earned rave reviews from his superiors during his time in the service, though there were glimpses into the madness that drove him to mass murder, according to records obtained exclusively by Fox News.

Aaron Alexis was described at different times during his 2007-2011 stint as a full-time Navy reservist as an "eager trainee" with "unlimited potential," who displayed a "get it done" attitude. The evaluations are in sharp contrast to fresher reports that detail a lengthy arrest record, mental illness and a pattern of harassing neighbors and strangers. They further complicate the emerging portrait of Alexis, who was working in IT for a Navy subcontractor when he died in the rampage at the Naval Sea Systems Command headquarters in Washington after first gunning down 12 civilian workers as they mustered for work in the cafeteria early in the morning.

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"Alexis has been onboard a short time and has established himself as a 'get-it-done' addition to the work center," wrote one evaluating supervisor in the spring of 2008. "Possesses unlimited potential and can become a valuable asset to the command with the proper guidance and self-discipline."

That report called Alexis, who was 34 when he died, a "talented technician" who meticulously carried out his duties as an aviation electrician's mate, working on aircraft electrical systems. It also praised him for work he did off the Georgia military base where he was stationed, calling him "community minded," and noting that he "dedicated over 10 hours of off-duty time to the Atlanta Food Bank distributing food to needy individuals in the metro Atlanta area."

A box on the review that read "must promote" was checked.

The review seemed at odds with a 2004 police report in Seattle, where Alexis shot out the tires of a construction worker's car in what he told police was an "anger-fueled blackout." He was arrested, but not prosecuted after promising to have no contact with the victim.

Another incident involving a gun led to his arrest in 2010, in Fort Worth, where he was stationed with the Navy. In that incident, he admitted shooting a gun through his ceiling and into the apartment of an upstairs neighbor. He told police he was "cleaning his gun," but the neighbor, who told police she'd had run-ins before with Alexis, was "terrified" according to police. Alexis was arrested, but prosecutors declined to pursue the case.

Alexis would be arrested in a DeKalb County, Georgia club for disorderly conduct months later, in August of 2008, an event that would later see him demoted one step in rank after missing a day of work while in jail.

Still, his next review praised him as a "proven technician" who was a "motivated" and "essential team member." That evaluation also recommended Alexis for promotion.

But in the spring of 2009, Alexis got his first negative review, based at least in part, on the Georgia arrest.

"[Alexis] has had a severe lapse in judgment on a number of occasions, and has been counseled several times for inappropriate conduct," stated the review, which went on to say he was "awarded Non Judicial Punishment in July of 2009."

Later that year, though, Alexis appealed the punishment and in December, the Navy granted his appeal, reinstated his rank and gave him back pay. The violation was essentially expunged from his record, one Navy official said. Subsequent reviews seemed to indicate he had put the incident behind him and was back to winning positive evaluations.

In February, 2010, his evaluation called him a "team player" and a "highly-motivated technician, an asset to the Avionic Division and Aircraft Maintenance Efforts."

"[Alexis] continues to displays (sic) great strides and a determination to excel," it read. "A future key asset to the Command's continued mission success. On track for AE2!"

Alexis was discharged in January 2011. A post-separation evaluation - the last review the U.S. Navy would give on the man who turned out to be a ticking time bomb - served as a reference to prospective employers in the private sector.

"A competent mechanic who possesses the potential to achieve great things," it read. "Alexis will be a valuable asset to any civilian organization."