Fort Hood Gunman 'Showed No Signs Of Violence'

An argument with one or more soldiers is likely to have preceded the Fort Hood shooting that left four men dead, including the gunman, officials have said.

Investigators are still trying to determine why 34-year-old Specialist Ivan Lopez killed three fellow soldiers and injured 16 others before turning the gun on himself.

But Lieutenant General Mark Milley said there is a "strong possibility" Lopez had a "verbal altercation" before going on a rampage, though it does not appear he targeted specific soldiers.

Lt Gen Milley, the senior officer at Fort Hood in Texas, urged caution against speculating on any possible motive until the investigation had run its course.

Investigators are also focusing on Lopez's mental health.

"We have very strong evidence that he had a medical history that indicates unstable psychiatric or psychological condition," Lt Gen Milley said.

"We believe that to be a fundamental, underlying cause."

Lopez had sought help for depression and other problems, and had been having tests for post-traumatic stress disorder.

On Thursday, investigators searched Lopez's home and questioned his wife.

Suzie Miller, who lived in the same apartment complex as Lopez, said few in the area knew him and his wife well because they had just moved in a few weeks ago.

She said: "I'd see him in his uniform heading out to the car every morning. He was friendly to me and a lot of us around here."

Earlier, US Army Secretary John McHugh said there was no indication that Lopez was involved with extremists.

He had shown no signs of violence or suicidal tendencies before the attack, Mr McHugh said.

Lopez was from the US territory of Puerto Rico and joined the island's National Guard in 1999.

He went on a peace and security mission to Egypt's Sinai Peninsula in the mid-2000s, and left the National Guard in 2010 to join the Army.

He arrived at Fort Hood in February from another military base in Texas, and was assigned to the 13th Sustainment Command (Expeditionary) at Fort Hood, which is a logistics and support unit.

He served for four months in Iraq in 2011, but did not see combat, officials said.

He was not wounded in action while serving overseas, but self-reported a traumatic brain injury when he returned to the US.

According to Lt Gen Milley's account, Lopez walked into a building and began firing a .45-calibre semi-automatic pistol, which was not registered with post authorities as required.

He then got into a vehicle and continued firing before entering another building, but he was eventually confronted by military police in a parking lot.

At that point the gunman put his gun to his head and pulled the trigger a final time.

The incident was the second deadly shooting at Fort Hood in five years after 13 people were killed at the base in 2009 by Army psychiatrist Major Nidal Hasan, who faces the death penalty.

President Barack Obama said he was "heartbroken" that the base had suffered again.

"Obviously this reopens the pain of what happened at Fort Hood five years ago. We know these families; we know their incredible service to this country and the sacrifices they make," the president said.