Aaron Alexis, the man who shot dead 12 people at a U.S. Navy base in Washington, had been treated for paranoia and reportedly heard voices in his head.
Family members told investigators on September 17 that 34-year-old Alexis was being treated for mental problems.
Alexis was a former navy reservist.
He arrived at the base where the Naval Sea Systems Command Headquarters building is located early on September 16 armed with an assault rifle and shotgun and apparently had a card granting him access to buildings.
He was shot and killed in an exchange of fire with police.
Investigators are still trying to determine a motive for the rampage.
U.S. Defense Secretary Chuck Hagel honored the victims of the shooting by laying a wreath at the U.S. Navy Memorial in Washington on September 17.
At the time of the shooting, Alexis worked for the Experts, a subcontractor hired to refresh equipment used on the Navy Marine Corps Intranet network.
The U.S. Navy said the suspect was formerly a petty officer 3rd class who served full-time in the naval reserve between 2007 and 2011.
Reports say he was a Buddhist convert who had previous gun-related brushes with the law.
Based on reporting by BBC and AFP