A gunman who shot dead three people and wounded 16 others at a US army base before committing suicide, was an Iraq War veteran who was being treated for mental illness, officials say.
The attack was at the Fort Hood base in Texas, where gunman Nidal Hasan killed more than a dozen people in 2009.
Within hours of Wednesday’s attack, investigators started looking into whether the man’s combat experience had caused lingering psychological trauma. Fort Hood’s senior officer, Lt Gen Mark Milley, said the gunman had sought help for depression, anxiety and other problems.
Among the possibilities investigators planned to explore was whether a fight or argument on the base triggered the attack.
“We have to find all those witnesses, the witnesses to every one of those shootings, and find out what his actions were, and what was said to the victims,” said a federal law enforcement official.
He said authorities would begin by speaking to the man’s wife, and expected to search his home and any computers he owned.
The shooter was identified as Ivan Lopez by Texas Rep Michael McCaul, chairman of the House Homeland Security Committee. But the congressman offered no other details, and the military declined to identify the gunman until his family members had been notified.
Lopez apparently walked into a building and began firing a .45-calibre semi-automatic pistol. He then got into a vehicle and continued firing before entering another building, but he was eventually confronted by military police in a car park, according to Gen Milley.
As he came within 20 feet (six metres) of an officer, the gunman put his hands up but then reached under his jacket and pulled out his gun. The officer drew her own weapon, and the suspect put his gun to his head and pulled the trigger a final time.
The gunman, who served in Iraq for four months in 2011, had been undergoing an assessment before the attack to determine if he had post-traumatic stress disorder, Gen Milley said.
He arrived at Fort Hood in February from another base in Texas. He was taking medication, and there were reports that he had complained after returning from Iraq about suffering a traumatic brain injury, Gen Milley said. The commander did not elaborate.
The gunman was never wounded in action, according to military records, and there was no indication the attack was related to terrorism. His weapon had been recently bought in the local area and was not registered to be on the base.
Those injured were taken to the base hospital and other local hospitals. At least three of the nine patients were listed in critical condition.
The attack immediately revived memories of the 2009 shooting rampage on Fort Hood, the deadliest attack on a domestic military installation in US history. Thirteen people were killed and more than 30 were wounded.
President Barack Obama vowed a complete investigation. In a hastily arranged statement while in Chicago, Mr Obama reflected on the sacrifices Fort Hood troops have made – including enduring multiple tours to Iraq and Afghanistan.
“They serve with valour. They serve with distinction, and when they’re at their home base, they need to feel safe,” he said. “We don’t yet know what happened tonight, but obviously that sense of safety has been broken once again.”