Police in Washington, D.C. are looking for the reason a military contractor went on a shooting rampage Monday at a U.S. naval facility, leaving 13 people dead, including the gunman.
Officials say they have found no connection to international terrorism and have found no manifesto or other writings suggesting a political or religious motivation.
But U.S. law enforcement officials told The Associated Press 34-year-old Aaron Alexis had paranoia and a sleep disorder and was hearing voices in his head. The investigators said family members told them Alexis had been treated since August by the Veterans Administration for his mental problems.
The Navy had not declared the contract employee mentally unfit, which would have rescinded his valid pass to get into the Washington Navy Yard. Once inside Monday, Alexis opened fire on employees at the Naval Sea Systems Command, using a shotgun, a military-style automatic assault rifle, and a handgun he is believed to have taken from a wounded security officer.
Washington Mayor Vincent Gray said in addition to the dead, eight people were hurt in Monday's incident. All are expected to survive.
Police released the identities of those killed late Monday night, with their ages ranging from the late 40s to early 70s.
Alexis is a New York City native and a resident of Fort Worth, Texas. News outlets say Alexis was previously arrested in two separate shooting incidents, once in 2004 in Seattle and the second in Fort Worth in 2010.
Late Monday, grieving residents gathered outside the Naval Yard and held a silent candlelight vigil.
U.S. President Barack Obama has ordered all flags across the country to fly at half-staff through sunset Friday to honor the victims. During an event at the White House Monday, Mr. Obama lamented yet another mass shooting, which he called a "cowardly act.''