Washington gunman Alexis had history of mental problems

The former Navy reservist who slaughtered 12 people at the Washington Navy Yard had been “hearing voices” and was being treated for mental problems in the weeks before the shooting rampage, but was not stripped of his security clearance, officials said.

Aaron Alexis, a 34-year-old information technology employee with a defence contractor, used a valid pass to get into the highly secured installation and started firing inside a building, the FBI said. He was killed in a gun battle with police.

The motive for the mass shooting — the deadliest on a military installation in the US since the attack at Fort Hood, Texas, in 2009 — was a mystery, investigators said.