A day after a mass shooting at Fort Hood, Texas, military post killed at least 13 people and wounded 30 others including himself, investigators on Friday sought to learn why an Army psychiatrist might have carried out the assault.
Maj. Nidal Malik Hasan, 39, allegedly opened fire Thursday afternoon at the post's Soldier Readiness Center, where troops deploying to Iraq and Afghanistan receive last-minute medical checkups.
The gunman shouted "Allahu Akbar!" before opening fire, Lt. Gen. Robert Cone, the post commander, told NBC's Today show Friday. The comment is Arabic for "God is great!"
Military investigators are trying Friday to determine the motive behind the mass shooting, the deadliest ever at a military facility in the United States. Hasan remained hospitalized, unconscious and on a ventilator Friday; in the chaotic hours after the shooting, the military initially said he had been killed.
"He's stable in one of our civilian hospitals," Col. Steven Braverman, a post spokesman, said at a Friday morning news conference.
Cone told reporters Thursday that the suspect, armed with at least two handguns, one a semiautomatic, began the rampage around 1:30 p.m. local time.
Hasan was later shot four times by civilian police Sgt. Kimberly Munley, Cone said. Munley was in stable condition after being shot and wounded in the melee. Cone credited Munley with "an amazing and aggressive performance."
In Washington, a senior U.S. official said authorities at Fort Hood first thought one of the people shot and killed was the assailant, a mistake that delayed the identification of Hasan as a suspect.
"In the heat of the incident, there was a lot of confusion," Col. John Rossi explained at Fort Hood. "It was just a mistake."
Authorities said they immediately took three other U.S. soldiers into custody on suspicion that they were involved in the shooting but released them within hours of the shooting.
Initially, 12 people were reported dead, but officials said early Friday that a 13th person had died overnight. Officials said 27 people remained hospitalized.
Rossi said "approximately half" of the victims required surgery. Military officials declined to release any names of victims.
Video from the scene showed police patrolling the area with handguns and rifles, ducking behind buildings for cover. Sirens wailed as a woman's voice on the post's public-address system urged people to take cover. Schools on the post went into lockdown, and family members trying to find out what was happening inside found cell phone lines jammed or busy.
A tearful and frightened Allison Chamberlain, who is seven months pregnant, stood outside the post after the incident.
"My husband's on post. He was just supposed to be cleaning weapons all day," she told NPR.
Chamberlain, 19, said she was in a grocery store parking lot at the time of the shooting.
"I saw that first helicopter and I knew," she said. "I mean, there was SWAT everywhere, cops, ambulances — I couldn't call post, everything was blocked."
"This stuff just doesn't happen to you," she said. "They're supposed to be soldiers, brothers — there's a bond, you know. Why did they do this?"
Spc. Jerry Richard, 27, who works at the center but was not on duty during the shooting, said, "Overseas you are ready for it. But here, you can't even defend yourself."
A senior U.S. official told The Associated Press that investigators have not ruled out the possibility that some casualties may have been victims of "friendly fire," shot by authorities amid the mayhem and confusion at the scene.
"Investigators are analyzing that right now," Rossi said.
In a statement issued by a public relations firm Thursday, Hasan's first cousin, Nader Hasan, said Nidal Hasan was born in Arlington, Va., and went to local high schools before attending Virginia Tech. Nader Hasan said he spoke for the family because Nidal Hasan's parents are no longer alive.
"We are shocked and saddened," he said in the statement, adding that the family is "filled with grief" over the casualties.
The suspect was a psychiatrist at Walter Reed Army Medical Center for six years before being sent to Texas in July. He was apparently upset about being scheduled to deploy overseas, according to Sen. Kay Bailey Hutchison of Texas, who told Fox News that she was told Hasan may have been targeting specific individuals.
A source told NPR's Joseph Shapiro that Hasan was put on probation early in his postgraduate work at the Uniformed Service University of the Health Sciences in Bethesda, Md. He was disciplined for proselytizing about his Muslim faith with patients and colleagues, according to the source, who worked with him at the time.
A neighbor of Hasan's, Patricia Villa, told the Associated Press that he had cleaned out his apartment in the days before the attack and offered her some items, including a copy of the Quran. She said he told her that he was being deployed on Friday.
The FBI, local police and other agencies searched Hasan's apartment Thursday night after evacuating the complex in Killeen, Texas, said city spokeswoman Hilary Shine. She referred questions about what was found to the FBI. The FBI in Dallas referred questions to a spokesman who was not immediately available early Friday morning.
The Associated Press reported that Hasan came to the attention of law enforcement at least six months ago because of Internet postings tied to him about suicide bombings and other threats.
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, attacks and that 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."
In Washington on Thursday, President Obama expressed his sympathies to the wounded and the families of the slain soldiers, and he pledged a full inquiry.
Islamic groups were also quick to condemn the killing after it became clear that the suspected shooter was Muslim. The Council of American-Islamic Relations issued a statement calling it a "cowardly" attack.
Fort Hood, which covers some 335 square miles near Killeen, is a prime deployment point for the conflicts in Afghanistan and Iraq. Roughly half of Fort Hood's 44,000 soldiers were serving in Iraq or Afghanistan as of August 2009.
More than 520 soldiers from Fort Hood have been killed since the U.S. invasions of Iraq and Afghanistan.
Killeen was the site of one of the nation's worst mass shootings. On Oct. 16, 1991, George Hennard shot and killed 23 people in a Luby's Cafeteria restaurant before turning the gun on himself. He also wounded 20 people.
