I'm not violent, navy yard gunman Aaron Alexis told doctors a month before murders

Aaron Alexis, the Washington naval yard gunman, insisted to doctors that he was not depressed or violent less than a month before murdering 12 people, it emerged yesterday (Thursday).

Details of the 34 year-old's treatment under a veterans' health programme were disclosed as fresh questions were raised about how the US government missed "red flags" indicating his mental instability.

The Department of Veterans Affairs said that Alexis, a former navy reservist who became a civilian contractor, had gone to casualty twice in recent weeks complaining of acute insomnia.

He was treated with trazodone, an antidepressant, but doctors at the Veterans Affairs hospitals apparently accepted his claim that he was not thinking of harming himself or others.

"Mr Alexis was alert and oriented, and was asked by VA doctors if he was struggling with anxiety or depression, or had thoughts about harming himself or others, which he denied," the department said in a statement.

Alexis's passage through the hospitals was among several incidents in recent months when the authorities appear to have missed signs that his mental health was deteriorating.

On August 7 he called police to a hotel in Providence, Rhode Island, in a state of panic and told officers that he was being followed by three people who were sending microwaves through his body.

Local police informed the navy's own police of their concerns about Alexis's mental state, faxing over details of their encounter to a naval station in nearby Newport.

However, navy authorities there never passed the message on to the Pentagon, where a decision could have been made to revoke Alexis's security clearance, the New York Times reported.

Just over a month after the incident in Rhode Island, Alexis used his contractor's work pass to enter the navy yard legitimately and walk past guards with a shotgun in his bag.

"Obviously there were a lot of red flags," Chuck Hagel, the secretary of defence, said. "Why they didn't get picked up, why they didn't get incorporated into the clearance process, what he was doing, those are all legitimate questions that we're going to be dealing with." Alexis reportedly created a webpage with the name "Mohammed Salem" but never used the site and investigators said they did not believe the shooting was linked to violent religious extremism.