US gunman had mental problems

Aaron Alexis’s motive in the Navy Yard rampage remained a mystery during the day, but law enforcement officials later revealed that he had paranoia and a sleep disorder and had been hearing voices.

They also said there had been no connection to international or domestic terrorism, and investigators had found no manifesto or other writings suggesting a political or religious motivation.

Family members said that Alexis, 34, who was shot dead by police, had been treated for his mental problems since August.

Alexis was an employee with a company that was a Defence Department subcontractor on a Navy-Marine Corps computer project.

He had been a full-time Navy reservist from 2007 to early 2011, and had a string of misconduct problems but received an honourable discharge.

He had complained about the Navy and of being a victim of discrimination and had several incidents with law enforcement, including two shootings.

A convert to Buddhism who grew up in New York City, after the shooting incidents in 2004 and 2010 in Fort Worth and Seattle, Alexis was portrayed in police reports as seething with anger.

It also emerged that the US Navy had not declared the defence contract employee mentally unfit, which would have rescinded the security clearance that Alexis had from his earlier time in the Navy Reserves.

Consequently, he a valid contractor’s pass to get into the Washington Navy Yard.

The attack – the seventh mass shooting during Barack Obama’s presidency – was also considered unlikely to lead to tighter gun controls.

President Barack Obama lamented “yet another mass shooting” and promised to make sure “whoever carried out this cowardly act is held responsible”.

The White House has been powerless to get gun control legislation passed by Congress.

The most recent measures – proposed during national outrage over a school shooting in December that killed 20 children – failed to win support from legislators earlier this year despite widespread public backing.

Monday’s onslaught at a single building at the highly secure Navy Yard began at about 8.20am.

The waterside base, in the US capital city, is about four miles southeast of the White House and the US Capitol.

Alexis carried three weapons in the attack: an AR-15 assault rifle, a shotgun, and a handgun that he took from a police officer at the scene.

The AR-15 is the same type used in last year’s mass shooting at a Newtown, Connecticut, school that killed 20 pupil and six staff.

The weapon was also used in the shooting at a Colorado cinema that killed 12 and wounded 70.

For much of the day, authorities said they were looking for a possible second attacker who may have been disguised in an olive-drab military-style uniform.

However, officers later they said they were convinced the shooting had been the work of a lone gunman, and the lockdown around the area was eased allowing Navy Yard employees to be gradually released from the complex while children were let out of nearby schools.

The FBI took charge of the investigation.

The dead ranged in age from 46 to 73.

Some were civilian employees and contractors, rather than active-duty military personnel.

Witnesses described how Alexis opened fire from a fourth-floor vantage point, aiming down on people on the main floor, which includes a glass-walled cafeteria.