Two days after Aaron Alexis shot and killed 12 people at the Washington Navy Yard, investigators are still struggling to find a motive as a more complete, and disturbing, profile of Alexis's mental health problems has emerged, including a report that he believed men were following him with a "microwave machine" to disrupt his sleep.

Following news that he heard voices and suffered from paranoia comes a separate report that in August, Alexis told Rhode Island police that a trio of unidentified men were using secret machines to talk to him through hotel walls and disrupt his sleep. According to the police report, Alexis said the incident began after he got into an argument with someone as he boarded a flight from Virginia to Rhode Island. That person, Alexis said, retaliated by sending three men to harass him.

Alexis said he changed hotels several times but could still hear the voices of the three men, who he said were “using 'some sort of microwave machine' to send vibrations through the ceiling, penetrating his body so he cannot fall asleep."

Police in Rhode Island say they contacted the Rhode Island naval base and forwarded the police report. A spokesperson from the base declined to comment to the Associated Press, but officials told the Washington Post that Alexis was treated at two VA hospitals after the Rhode Island incident.

Thomas Hoshko, chief executive of The Experts and Alexis's employer, told the Washington Post he wouldn't have hired Alexis if he'd known of his legal and mental health problems

“Anything that suggest criminal problems or mental health issues, that would be a flag,” Hoshko said. “We would not have hired him.”

Two weeks later, Alexis moved to Washington DC for his job with The Experts as contractor at the Navy Yard. Not long after, he used an out-of-state ID to legally purchase a shotgun—the same gun he reportedly used during Monday's shooting—at a DC-area gun store, where he passed a federal background check. The purchase has raised questions about the ability of someone with such well-documented legal and mental health issues buying a gun. From the Associated Press:

It is illegal for gun dealers to sell handguns to such out-of-state buyers, but the Firearms Owners' Protection Act, passed by Congress in 1986, opened up interstate sales for shotguns and rifles. Virginia gun laws require only that an out-of-state buyer show valid identification, pass a background check and otherwise abide by state laws in order to buy a shotgun in the state. Alexis was never prosecuted for the two misdemeanors involving guns.

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Federal gun laws bar the mentally ill from legally buying guns from licensed dealers. But the law requires that someone be involuntarily committed to a mental health facility or declared mentally ill by a judge, and that information must be reported to the FBI in order to appear on a background checks. In the wake of the 2007 shooting at Virginia Tech, state authorities changed state laws to make it tougher for the mentally ill to buy guns there.

But like other recently accused mass shooters, Alexis was never declared mentally ill by a judge or committed to a hospital. He was being treated by the Veterans Administration as recently as August, according to two law enforcement officials, but the Navy had not declared him mentally unfit.

Meanwhile, law enforcement officers still haven't found a clear motive for the attack. Officials told the Associated Press that they have found no manifesto, political or otherwise, or any other evidence explaining why the shooting took place.

[Image via AP]