A US soldier with mental health issues shoots dead three people and injures at least 16 before shooting himself at an army base in Fort Hood, Texas.
The soldier, who was being treated for depression and anxiety, went to two buildings on the base and opened fire before he was confronted by military police, Fort Hood commanding officer Mark Milley said.
The gunman, whose motive remains unknown, then shot himself in the head with a .45-caliber pistol, he added.
“At this time there is no indication that this incident is related to terrorism,” Mr Milley told a news conference.
The rampage is the third shooting at a military base in the United States in about six months.
It comes amid a broader national debate over the extent of gun control regulations after a series of shootings in public places, such as schools and malls.
Watch: inside Fort Hood - the soldiers' stories
US media named the suspect as Ivan Lopez, 34, however officials were waiting to notify his family before releasing his name. The suspect’s wife was cooperating with officials, according to CNN.
The gunman had served for four months in Iraq in 2011, officials said, and was also undergoing evaluation for post-traumatic stress disorder.
The Scott and White hospital in Temple, Texas, where some of the wounded were taken, said nine patients were in intensive care, three in critical condition.
Other victims were taken to Fort Hood’s Carl R. Darnall army medical centre, nearby where the shooting occurred.
US President Barack Obama said he was “heartbroken” that another shooting had occurred at the Fort Hood army base.
“We are going to get to the bottom of exactly what happened,” Mr Obama said. “We’re heartbroken that something like this might have happened again.”
The latest shooting at Fort Hood is throwing a spotlight on the US military’s so-far frustrated efforts to secure its bases from potential shooters, who increasingly appear to see the facilities as attractive targets.
The violence echoed the rampage of 2009, when a former army psychiatrist shot dead 13 people and wounded 32 others in a shooting spree at Fort Hood, a base from where soldiers prepare to deploy to Iraq and Afghanistan.
Major Nidal Hasan shouted “Allahu Akbar”, Arabic for “God is greatest”, during the attack and later said he wanted to be a martyr. He was convicted and faces death by lethal injection.
In February, the US military demolished the building where Hasan went on his shooting spree and plans to plant trees, install a gazebo and mark the site with a remembrance plaque.
“It was just like a kick in the gut. It made me sad, it made me angry. It made me want to do something to help,” Killeen Mayor Daniel Corbin told CNN, responding to a question about another burst of violence on the sprawling base.
In September, a gunman opened fire at the Washington Navy Yard, killing 12 and wounding four before being killed by police. Last month, a civilian shot dead a sailor aboard a ship at a US navy base in Norfolk, Virginia.