Education: 1997 graduate of Virginia Tech University. Received doctorate in psychiatry from the Uniformed Services University of the Health Sciences in Bethesda, Md.
Career: U.S. Army psychiatrist. As of Oct. 13, he had less than a year of clinical practice. From 2003 through this summer, was an intern, a resident and then a fellow at Walter Reed Army Medical Center in Washington D.C. Also, he was listed by the Center for the Study of Traumatic Stress as a fellow for disaster and preventive psychology.
Commissioned as a captain, he was promoted to major in May.
He passed tests in September: He showed no sign of physical or mental problems in examinations as recent as September.
Personal information: He was single and had no children. His former imam Faizul Khan said of his search for a marriage partner: "I don't think he ever had a match [at the mosque], because he had too many conditions. He wanted a girl who was very religious, prays five times a day, which is all very good."
He has two brothers, one living in Virginia and another in Jerusalem, his cousin Nader Hasan said.
Religion: He attended the Muslim Community Center in Silver Spring, Md., and was devout, Khan said. He attended prayers at least once a day, seven days a week, often in his Army fatigues, Khan said.
July 18: Specialist Ryan Richard Schlack, of Oshkosh, Wis., was fatally shot at a party at Fort Hood. A fellow soldier, Specialist Armando Baca, is charged with the murder.
May 11: Sgt. John M. Russell, who was on his third overseas deployment, allegedly opened fire at a military counseling clinic at a Baghdad army base. He is charged with killing five U.S. service members.
Sept. 8, 2008: Specialist Jody Michael Wirawan, 22, of Eagle River, Ala., who was to soon be discharged, fatally shot 1st Lt. Robert Bartlett Fletcher, 24, of Jensen Beach, Fla., at Fort Hood. He then shot himself.
Sept. 14, 2008: Sgt. Joseph Bozicevich, 39, of Minneapolis, allegedly fatally shot a superior and a fellow team leader at their Army patrol base in central Iraq. The two slain soldiers had been giving Bozicevich a critique about performance problems before he shot them, witnesses said.
September 2007: Army Cpl. Timothy Ayers was sentenced to two years and four months in prison after pleading guilty to involuntary manslaughter in the 2007 shooting of his platoon sergeant in Iraq.
November 2006: Specialist Chris Rolan, an Army medic, was sentenced to 33 years in prison in 2007 for killing a fellow soldier in November 2006 after a night of heavy drinking in Iraq.
March 23, 2003: Army Sgt. Hasan Akbar threw grenades into tents occupied by fellow members of the 101st Airborne Division, killing two officers and wounding 14 soldiers in Kuwait.
Military prosecutors said that Akbar, who was ultimately sentenced to death, was motivated by anger at the deaths of Iraqi civilians at the hands of U.S. troops.
Fort Hood is the largest active-duty armored post in the United States. Home to about 52,000 troops as of earlier this year, the sprawling 339-square-mile base is located outside Killeen, Texas, halfway between Austin and Waco.
Fort Hood opened on Sept. 18, 1942, and was named in honor of Gen. John Bell Hood. It has been continuously used for armored training and is charged with maintaining readiness for combat missions. Today, the fort serves as a home for Headquarters III Corps, First Army Division West, the 1st Cavalry Division, 4th Infantry Division's Combat Aviation Brigade, 13th Corps Support Command, 89th Military Police Brigade, 504th Battlefield Surveillance Brigade, 21st Cavalry Brigade (Air Combat), 4th Combat Aviation Brigade and 31st Air Defense Brigade.