Washington gunman was former Navy officer

A gunman who died after killing 12 people at a naval installation in Washington DC has been identified as a former Navy serviceman.

Aaron Alexis, 34, died in a gun battle with police during the rampage at Washington Navy Yard yesterday.

Eight others were injured in the attack, which began at around 12:20pm.

US President Barack Obama ordered flags be lowered to half mast at the White House and on Capitol Hill.

He said he mourned "yet another mass shooting" and condemned the "cowardly act".

No motive is known for the attack, whose dozen victims ranged in age from 46 to 73, said the authorities.

Police initially responded to reports of two other armed suspects, but after exhaustive searches Washington Police Chief Cathy Lanier said on Monday night they were all but certain that Alexis was the only gunman.

Witnesses said the suspect sprayed bullets in a hallway and fired from a balcony down on to workers in an atrium at the heavily secured installation in the US capital.

Alexis was formerly a petty officer 3rd class who served full-time in the naval reserve from 2007-11, said the US Navy.

It was not immediately clear why he left the military, but unnamed military officers told US media there had been a series of misconduct issues during his service.

According to media reports, Alexis was a Buddhist convert who had two previous gun-related brushes with the law.

In 2004 he was arrested in Seattle for shooting a construction worker's car tyres, in what he described as an enraged "black-out".

And he was questioned by Fort Worth police in 2010 after firing his gun through the floor of an upstairs apartment. He said it was an accidental discharge.