Authorities say Fort Hood shooting Nidal Malik Hasan remains in a coma but is expected to live.
A federal law enforcement official said investigators have not been able to talk to Hasan since the deadly rampage that left 13 people dead and injured 30 others at the sprawling Army post in Texas on Thursday.
The initial investigation shows that Hasan allegedly used only one gun during the attack -- a 5.7-caliber semiautomatic pistol.
Army officials said Hasan also was carrying another handgun. But the law enforcement official said there's nothing so far to indicate the second weapon was fired.
The law enforcement official spoke on condition of anonymity because the investigation is ongoing.
THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.
WASHINGTON (AP) -- His name appears on radical Internet postings. A fellow officer says he fought his deployment to Iraq and argued with soldiers who supported U.S. wars. He required counseling as a medical student because of problems with patients.
There are many unknowns about Nidal Malik Hasan, the man authorities say is responsible for the worst mass killing on a U.S. military base. Most of all, his motive.
For six years before reporting for duty at Fort Hood, Texas, in July, the 39-year-old Army major worked at the Walter Reed Army Medical Center pursuing his career in psychiatry, as an intern, a resident and, last year, a fellow in disaster and preventive psychiatry. He received his medical degree from the military's Uniformed Services University of the Health Sciences in Bethesda, Md., in 2001.
While an intern at Walter Reed, Hasan had some "difficulties" that required counseling and extra supervision, said Dr. Thomas Grieger, who was the training director at the time.
Grieger said privacy laws prevented him from going into details but noted that the problems had to do with Hasan's interactions with patients. He recalled Hasan as a "mostly very quiet" person who never spoke ill of the military or his country.
"He swore an oath of loyalty to the military," Grieger said. "I didn't hear anything contrary to those oaths."
But, more recently, federal agents grew suspicious.
At least six months ago, Hasan came to the attention of law enforcement officials because of Internet postings about suicide bombings and other threats, including posts that equated suicide bombers to soldiers who throw themselves on a grenade to save the lives of their comrades.
They had not determined for certain whether Hasan is the author of the posting, and a formal investigation had not been opened before the shooting, said law enforcement officials who spoke on condition of anonymity because they are not authorized to discuss the case.
Federal authorities seized Hasan's computer Friday during a search of his apartment in Killeen, Texas, said a U.S. military official who spoke on condition of anonymity because of the ongoing investigation.
In an interview with The Washington Post, Hasan's aunt, Noel Hasan of Falls Church, Va., said he had been harassed about being a Muslim in the years after the Sept. 11, 2001, terror attacks and he wanted out of the Army.
"Some people can take it and some people cannot," she said. "He had listened to all of that and he wanted out of the military."
She said he had sought a discharge from the military for several years, and even offered to repay the cost of his medical training.
A military official told The Associated Press that Hasan was in the preparation stage of deployment, which can take months. The official said Hasan had indicated he didn't want to go to Iraq but was willing to serve in Afghanistan. The official did not have authorization to discuss the matter publicly and spoke on condition of anonymity.
A second military official said Hasan's family has Palestinian roots. There have been reports that he was harassed for his Muslim religion, but the official says there is no indication Hasan filed a complaint within the military about that.
Terrorism task force agents plan to interview several of Hasan's relatives Friday, according to a law enforcement official who spoke on condition of anonymity because the person was not authorized to discuss the case.
Noel Hasan said her nephew "did not make many friends" and would say "they military was his life."
A cousin, Nader Hasan, told The New York Times that after counseling soldiers returning from Iraq and Afghanistan with post-traumatic stress disorder, Hasan knew war firsthand.
"He was mortified by the idea of having to deploy," Nader Hasan said. "He had people telling him on a daily basis the horrors they saw over there."
Federal law-enforcement agents ordered an evacuation of the apartment complex where Hasan lived in Killeen, Texas, Thursday night and conducted a search of his home, said Hilary Shine, director of public information for the city. She didn't say what was found during the search.
Officials said earlier that federal search warrants were being drawn up to authorize the seizure of his computer.
Retired Army Col. Terry Lee, who said he worked with Hasan, told Fox News that Hasan had hoped President Barack Obama would pull troops out of Afghanistan and Iraq. Lee said Hasan got into frequent arguments with others in the military who supported the wars, and had tried hard to prevent his pending deployment.
Col. Kimberly Kesling, deputy commander of clinical services at Darnall Army Medical Center at Fort Hood, said she had known Hasan.
"You wouldn't think that someone who works in your facility and provided excellent care for his patients, which he did, could do something like this," Kesling said. She praised his work ethic, saying, "In my personal interactions, there was never any indication he would do something like this." Kesling described him as "a quiet man who wouldn't seek the limelight" and said she was 'shocked' when she heard that he was the man suspected of carrying out the shootings.
Hasan attended prayers regularly when he lived outside Washington, often in his Army uniform, said Faizul Khan, a former imam at a mosque Hasan attended in Silver Spring, Md. He said Hasan was a lifelong Muslim.
"I got the impression that he was a committed soldier," Khan said. He spoke often with Hasan about Hasan's desire for a wife.
On a form filled out by those seeking spouses through a program at the mosque, Hasan listed his birthplace as Arlington, Va., but his nationality as Palestinian, Khan said.
"I don't know why he listed Palestinian," Khan said, "He was not born in Palestine."
Nothing stood out about Hasan as radical or extremist, Khan said.
"We hardly ever got to discussing politics," Khan said. "Mostly we were discussing religious matters, nothing too controversial, nothing like an extremist."
Hasan earned his rank of major in April 2008, according to a July 2008 Army Times article.
He served eight years as an enlisted soldier. Military records show he also served in the ROTC as an undergraduate at Virginia Tech in Blacksburg and received a bachelor's degree in biochemistry there in 1997.
But college officials said Friday that Hasan graduated with honors in biochemistry in 1995 and there was no record of him serving in any ROTC program.
He previously had attended Barstow Community College in Barstow, Calif., and Virginia Western Community College in Roanoke, Va., according to Virginia Tech records.
Associated Press writers Lara Jakes, Pam Hess, Lolita C. Baldor and Brett Zongker in Washington; Alicia Chang in Los Angeles; and Sue Lindsey in Roanoke, Va., contributed to this report.