Four persons dead, 16 injured in US military base shooting

A soldier opened fire today at an enormous US army base in Texas that was the scene of a deadly shooting rampage in 2009, killing three persons and wounding 16 others before taking his own life.

The gunman, identified as Ivan lopez, 34, opened fire at two locations in Fort Hood -- inside a building housing a medical brigade and in a facility belonging to a transportation battalion -- prompting authorities to order a lockdown.

The suspect, a soldier who had served in Iraq, "had behavioural health and mental health" issues, the Army post's commander lt General Mark Milley said.

He said there was no known motive for the shooting.

"There is no indication that this incident is related to terrorism, although we are not ruling anything out," he said.

Milley said the incident began at the administration building for the medical brigade. The suspect then moved by car to the transport battalion.

"He was confronted by a military police officer and died of a self-inflicted gunshot wound to the head in a parking lot," he said.

Milley said the suspect was carrying a .45 calibre Smith and Wesson semi-automatic pistol bought recently in the local area and not registered with the base, as is required.

Another US official said the shooter was wearing combat fatigues. The lockdown was lifted at the base about five hours later.

US President Barack Obama expressed sorrow that tragedy had once again struck the base. "We're heartbroken that something like this might have happened again," the president said.

He promised to '"get to the bottom" of the latest incident.

"We are going to do everything we can to make sure that the community at Fort Hood has what it needs to deal with the current situation, but also any potential aftermath," he said.

The suspect, who served in Iraq for four months in 2011, had arrived in Fort Hood only in February, having moved from another installation in Texas.

In 2009, Fort Hood was the scene of the worst mass shooting ever to take place at a military base in the US. It left 13 people dead and more than 30 injured. The gunman, Major Nidal Hasan, a former army psychiatrist, was convicted by a military court and sentenced to death in August last year.

The shooting comes one day after the US Marine Corps confirmed an FBI search is underway for a former Army recruit, identified as Muhammed Abdullah Hassan or "Booker", who was plotting a "Fort Hood-inspired jihad against US soldiers."

Defence Secretary Chuck Hagel also was monitoring the situation. He described what happened as a "terrible tragedy."

According to the Fort Hood website, the post is one of the largest in the world with 45,414 assigned soldiers and 8,900 civilian employees.

The installation, which encompasses 214,000 acres, is home to two divisions -- the Army's 1st Calvary and the 4th Infantry (Mechanized). There are 12 other units attached or based there.

Obama, who was outside Washington when the shootout at an Army base in Texas happened, held a conference call with his national security team abroad Air Force One on his way back, the White House said.

Obama convened the conference call with the top Pentagon and FBI leadership to receive an update on the shooting at Fort Hood.

He commended the military personnel, first responders, and medical staff who responded swiftly and heroically to the horrific shooting.

During the call, Obama directed his team to utilize every resource available to fully investigate the shooting.

"As the President said earlier tonight, these brave men and women serve with valor and distinction, and when at home they need to feel safe," the White House said.

According to the White House, the Department of Defence has the lead on the investigation with support from federal partners including the FBI, as well as state and local law enforcement personnel.