Fort Hood shootings: US Army probes soldier's mental health
The US Army is investigating whether psychological trauma was the reason a soldier carried out a deadly shooting spree at a Texas military base.
The US Army identified the gunman as 34-year-old Specialist Ivan Lopez, originally from Puerto Rico.
Three people were killed and 16 others wounded before the gunman shot himself dead in the attack at Fort Hood.
Officials said the shooter had served in Iraq and was being assessed for post-traumatic stress disorder.
Fort Hood's commanding officer, Lt Gen Mark Milley, told reporters at a Thursday afternoon news conference: "We have very strong evidence that he had a medical history that indicates an unstable psychiatric or psychological condition… we believe that to be a fundamental, underlying causal factor."
He said earlier that Lopez had not been injured when he served in Iraq in 2011 but had sought treatment for depression, anxiety and other problems.
He had arrived at Fort Hood from another base in February and was taking medication, Lt Gen Milley said.
The shooting took place at two buildings on the base at about 16:00 local time (21:00 GMT) on Wednesday.
Lt Gen Milley said the gunman walked into one of the buildings and opened fire with a .45-calibre semi-automatic pistol.
He then got into a vehicle and continued firing before entering another building and opening fire again.
It was here that Lopez was eventually stopped by military police, shooting himself in the head when confronted by a female officer in the car park.
The shooting incident lasted between 15 and 20 minutes.
Nine of those injured are reported to be in intensive care, with three in critical condition.
At a previously scheduled congressional panel hearing, the US Army's top civilian official said the soldier accused in the shooting had been deployed but did not see combat, serving as a truck driver in the final months of the Iraq war.
Army Secretary John McHugh said the soldier had been examined by a psychiatrist in March and saw no "sign of any likely violence either to himself or others". He had been prescribed a sleeping drug, Ambien.
Officials say the weapon was bought in a local store and the soldier lived off base. Firearms are largely banned at US Army bases, with few soldiers besides military police allowed to carry them.
On Thursday in Washington, President Barack Obama said: "To see this unspeakable, senseless violence happen in a place where they're supposed to feel safe - home base - is tragic."
Fort Hood was the scene of a gun rampage in 2009 that left 13 soldiers dead and 32 wounded.
Major Nidal Hasan was sentenced to death last September for that attack - the deadliest on a domestic military installation in US history.
He said he opened fire to protect Taliban insurgents from US troops who were about to deploy to Afghanistan.
The building where the attack took place has only recently been demolished to make way for a place of remembrance.
Another US soldier, Naser Jason Abdo, was jailed for life for plotting to blow up a restaurant full of troops near Fort Hood in 2011.
The Texas native and Muslim convert said he had been inspired by Maj Hasan.
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