The main gate at the U.S. Army post at Fort Hood, Texas is pictured in this undated photograph, obtained on November 5, 2009
Four people were killed in a shooting at Fort Hood on Wednesday including the assailant, a soldier who served in Iraq and was being treated for mental health issues, the commander of the US base said.
"There is no indication that this incident is related to terrorism," Lieutenant General Mark Milley told reporters, adding that 16 people were wounded in the incident at the huge US army base in Texas, scene of a deadly shooting rampage in 2009.
The shooter - who was not identified pending notification of his next of kin - took his own life, Milley said.
All of the dead and wounded were military personnel.
The assailant used a .45-caliber Smith and Wesson semi-automatic pistol that he had bought recently in the area, the general said.
The shooter had spent four months in Iraq in 2011 and was currently undergoing a "diagnosis process" to determine if he was suffering from post-traumatic stress disorder (PTSD), Milley told reporters.
The sprawling military site was on lockdown for several hours as the incident unfolded, but the all-clear was given late Wednesday.
The Federal Bureau of Investigation, the Bureau of Alcohol, Tobacco, Firearms and Explosives, state police, local law enforcement and military police were all working on the investigation.