WASHINGTON (AP) — Investigators focused Thursday on the erratic behavior of a former U.S. Navy reservist who law enforcement officials say had reported hearing voices before he shot dead 12 people at a military base in Washington this week. The national conversation turned once again to mental health, and to gun control.

Monday's rampage lasted more than 30 minutes, unusually long for a mass shooting, and the Capitol Police, which protects members of Congress and Congressional buildings, has ordered an investigation into the force's response. Reports say a tactical response team arrived within minutes and was told by a supervisor to relax its state of alert. The base is less than three miles (4 kilometers) from the Capitol.

If the reports are accurate, "It would be an unbearable failure," Senate Sergeant at Arms Terrance Gainer said in an email.

Defense Secretary Chuck Hagel has ordered two reviews of military security and employee screening programs, acknowledging that "a lot of red flags" may have been missed in the background check of 34-year-old Aaron Alexis.

Alexis, who entered the base with a valid security badge, was killed in a shootout with police. The base reopened as normal Thursday.

The Department of Veterans Affairs said Alexis visited two hospitals in the weeks before the shooting but denied that he was depressed or had thoughts of harming himself or others.

Alexis complained of insomnia during an Aug. 23 emergency room visit to a VA Medical Center. He was given sleep medication and advised to follow up with a doctor. He made a similar visit five days later to the VA hospital in Washington. His medication was refilled.

Alexis appeared "alert and oriented," the VA said in a statement presented to lawmakers.

Two weeks before his ER visit, he complained to police in Rhode Island that people were talking to him through the walls and ceilings of his hotel room and sending microwave vibrations into his body to deprive him of sleep. Navy officials said the police reported the incident to officers at the local base security office, but nothing more was done because he did not appear to be a threat.

Alexis, who had interest in Buddhism and Thai language and culture, also visited a Buddhist temple in Massachusetts last month and talked about noises in his head. Eang Tan, a board member at the Thai Buddhist temple, said Alexis addressed temple members in fluent Thai and asked for a place to spend the night. He spent one night, then left.

Despite his past incidents with police over his gun use, Alexis maintained his security clearance as he arrived in Washington in late August for a job as an information technology employee at a defense-related computer company.

Alexis had been a full-time Navy reservist from 2007 to early 2011, and a Navy spokesman said his security clearance, at the "secret level," was good for 10 years from when he got it.

On Monday morning, he brought with him a legally obtained shotgun on which the cryptic messages of "better off this way" and "my ELF weapon" were scrawled, according to a law enforcement document reviewed by The Associated Press. The meaning of those words wasn't immediately clear.

Alexis's mother said Wednesday she does not know why her son opened fire.

The shotgun was brought into the building disassembled and pieced together by Alexis once inside, according to a law enforcement official and a senior defense official who spoke on the condition of anonymity because they were not authorized to discuss the matter publicly.

That firearm would not be covered under a previously proposed weapons ban supported by the White House.


Associated Press writers Eric Tucker, Kevin Freking, Lolita C. Baldor, Laurie Kellman, Alicia A. Caldwell and Eileen Sullivan in Washington contributed to this report.