Investigators are searching the home and questioning the wife of the soldier who went on the deadly shooting rampage at Fort Hood.
Fort Hood spokesman Chris Haug said the shooter lived with his wife and children locally after transferring from another military installation in Texas in February.
The shooter, identified as Ivan Lopez by Texas Rep. Michael McCaul, killed three and injured 16 on Wednesday before turning his privately owned .45-caliber handgun on himself.
Haug said more details may be released later in the afternoon.
Authorities say the gunman who opened fire at Fort Hood, killing three people and himself, was an Iraq War veteran being treated for mental illness.
Wednesday's attack also wounded 16 people at the Texas military base, where a 2009 shooting rampage killed 13 people and wounded more than 30.
A federal law enforcement official says investigators will interview the gunman's wife, search his home, and examine whether his combat experience caused lingering psychological trauma.
The official, who spoke to The Associated Press on condition of anonymity, says investigators also must find witnesses who know what the shooter said and did during the attack.
Fort Hood's senior officer, Lt. Gen. Mark Milley, says the gunman had sought help for depression and anxiety, and was being assessed for post-traumatic stress disorder.
(CNN) - Four people have died -- including the suspected shooter -- as a result of Wednesday's shooting at Fort Hood, said the Army post's commander, Lt. Gen. Mark A. Milley. He said 16 people were wounded at the installation in central Texas.
There was no known motive. "There is no indication that this incident is related to terrorism although we are not ruling anything out," Milley said.
The suspected shooter "had behavioral health and mental health" issues, according to Milley.
The suspect was engaged by military police before he fatally shot himself in the head, he said.
Four patients were being treated at Scott & White Hospital in Temple and two others will require surgery soon after being airlifted there. The patients' conditions range from "stable to quite critical," according to a hospital official.
Others were taken to Darnall Army Medical Center, not far from the Medical Brigade building where the shooting occurred, said a soldier who lives nearby and who spoke on the condition of anonymity.
The suspected shooter was wearing combat fatigues, according to a U.S. official briefed on the shooting. The suspect is believed to have used a semi-automatic handgun, officials told CNN.
President Barack Obama was briefed and said Wednesday evening "we're heartbroken something like this might have happened again."
He was referring to the November 2009 massacre.
"I want to just assure all of us we are going to get to the bottom of exactly what happened," the President said.
Defense Secretary Chuck Hagel also was monitoring the situation. He described what happened as a "terrible tragedy."
"We know there are casualties -- both people killed and injured. We don't have all the facts yet," Hagel told reporters in Honolulu.
Sheriff's deputies from Bell County and state troopers were assisting by securing the area around the post, according to Bell County Sheriff's Lt. Donnie Adams. Authorities in the town of Killeen, just outside the gates, were also standing by to help.
"We are very concerned. Fort Hood is always there for us and we want to be there for them," said Killeen Mayor Dan Corbin.
He continued: "They are used to dealing with combat situations, and I'm sure they are very capable of handling this."