US military base says 16 injured as gunman, who was receiving psychiatric help, went on shooting spree before killing himself

An Iraq war veteran being treated for mental illness opened fire on fellow service members at the Fort Hood military base in Texas, killing three people and wounding 16 before killing himself, at the same post where more than a dozen people died in a 2009 attack.

The shooter, who was named as Ivan Lopez, apparently walked into a building on Wednesday and began firing a .45-calibre semi-automatic pistol that had been purchased recently. He then got into a vehicle and continued firing before entering another building and kept shooting.

He was eventually confronted by military police in a parking lot. As he came within 20ft (6 metres) of an officer, the gunman put his hands up but then reached under his jacket and pulled out his weapon. The officer drew her own gun, and the suspect put his pistol to his head and pulled the trigger.

The gunman, who was married and served in Iraq for four months in 2011, had sought help for depression, anxiety and other problems. Before the attack he had been undergoing an assessment to determine whether he had post-traumatic stress disorder, according to Lieutenant General Mark Milley, the senior officer on the base.

Milley said the incident began about 4pm local time (10pm BST) at an administration building for a medical brigade. "At this time there is no indication that this incident is related to terrorism although we are not ruling anything out and the investigation continues," he said.

A soldier and his wife reflect on the news. Photograph: Deborah Cannon - American-States/Reuters

The lockdown was lifted at the base about five hours later. Milley said he did not want to confirm the suspect's name at the briefing because his next of kin had not been identified. However, he said the shooter was married and was undergoing treatment for "depression, anxiety and a variety of other psychiatric and psychological issues".

He said the suspect had arrived in Fort Hood in February, having moved from another installation in Texas.

As the shootings unfolded, the base's Twitter feed had urged personnel to "shelter in place". The First Calvary Division, which is based at Fort Hood, sent a Twitter alert telling people on base to close doors and stay away from windows.

About an hour later, the base issued a statement confirming the incident: "There has been a shooting at Fort Hood, and injuries are reported. Emergency crews are on the scene. No further details are known at this time."

A lieutenant from Bell County sheriff's office, Donnie Adams, said they had dispatched deputies and troopers from the Texas department of public safety to the base after receiving reports of an "active shooter". FBI spokeswoman Michelle Lee said its agents were also dispatched to the scene.

Barack Obama, in Chicago on a fundraising tour, expressed sorrow that tragedy had once again struck the base. "We're heartbroken that something like this might have happened again," he said.

Obama promised to get to the bottom of the latest incident. "Obviously this reopened the pain of what happened at Fort Hood five years ago. We know these families, we know the service to their country and the sacrifices that they make."

Barack Obama makes a statement about the shooting at Fort Hood. Photograph: Larry Downing/Reuters

In 2009, Fort Hood was the scene of the worst mass shooting at a military base in the US. The massacre on 5 November occurred at a processing centre where troops preparing to deploy to Afghanistan were receiving medical checkups. It left 13 dead and more than 30 injured. The gunman, Nidal Hasan, a former army psychiatrist, was convicted by a military court and sentenced to death in August.

In 2011, Naser Jason Abdo was arrested for planning a bomb attack on a restaurant frequented by Fort Hood personnel. An awol soldier at the time, he was sentenced to life in prison the following year.

After the 2009 shooting, the US military tightened security at bases nationwide. But last September, a naval contractor, Aaron Alexis, opened fire at the Washington navy yard, leaving at least 13 people dead, including the gunman. After that shooting, the defence secretary, Chuck Hagel, ordered the Pentagon to review security at all US defence installations worldwide and examine the granting of security clearances that allow access to them.

"When we have these kinds of tragedies on our bases something's not working. We'll identify it, we'll get the facts and we'll fix it," Hagel told reporters at a briefing in Honolulu on Wednesday, where he was meeting defence ministers from Asian countries.

General Martin Dempsey, the chairman of the joint chiefs of staff, said in a statement: "Our thoughts and prayers are with the Fort Hood community in the aftermath of this tragedy. Many questions remain and our focus is on supporting the victims and their families … This is a community that has faced and overcome crises with resilience and strength."

Sprawling over 214,000 acres, Fort Hood is one of the largest army bases in the world, home to more than 45,000 soldiers and 8,900 civilian staff.