The gunshots came out of the blue.

An Army psychiatrist, trained to treat soldiers under stress, allegedly opened fire yesterday in a crowded medical building at Fort Hood, Texas. When the assault ended minutes later, the attack had become what is believed to be the largest mass shooting to occur on a U.S. military base. Twelve were killed, 31 wounded.

Nidal Malik Hasan, a major who had made a career in the military, allegedly fired a pair of pistols, one of them semiautomatic, dropping and scattering people as they waited to see doctors, according to authorities. Hasan and a policewoman reportedly exchanged fire. Both were hit. Both survived.

When the gunfire stop-ped, soldiers schooled in battlefield medicine ripped their clothes to make tourniquets and bandages. Someone hustled to seal off an auditorium at the Soldier Readiness Center, where 138 troops were marking their graduation from college. Sirens typically used to warn of tornados sweeping across the plains alerted residents, schools locked down and the Fort Hood community struggled to understand what had just happened.

Hasan, initially reported killed, was in stable condition at a hospital under military guard, said Lt. Gen. Bob Cone at Fort Hood. Hasan was shot four times, and was on a ventilator and unconscious, military officials said.

"I would say his death is not imminent," Cone said.

Still unexplained last night was the motive for Hasan's attack. Asked if it could be considered a terrorist attack, Cone replied, "I couldn't rule that out" but said the evidence does not point to that.

In Iraq, an Army journalist telephoned his wife, who lives on the base. When she did not answer, he turned to e-mail. She said there had been shootings and an order to secure all doors and windows.

"This is ridiculous," Naveed Ali Shah, the soldier, told his wife. "I'm in the war zone, not you!"

The accused gunman is a 39-year-old Virginia-born doctor who once practiced at Walter Reed Army Medical Center in the nation's capital. The motive remains unclear, although some sources reported the suspect is opposed to U.S. involvement in Afghanistan and Iraq and upset about an imminent deployment.

"We are shocked and saddened by the terrible events at Fort Hood today," his cousin, Nadar Hasan, said in a statement issued on behalf of their family. "We send the families of the victims our most heartfelt sympathies."

'IT'S STUNNING'

The attack erupted shortly after lunchtime on the sprawling complex that has absorbed more than 500 fatalities in Iraq and Afghanistan, more than any other base. Investigators said their initial impression was that the gunman had acted alone.

"It's a terrible tragedy. It's stunning," Cone said. "Soldiers and family members and many of the great civilians who work here are absolutely devastated."

The Soldier Readiness Center holds hundreds of people and is one of the most populated parts of the base, said Steve Moore, a spokesman for III Corps at Fort Hood. Nearby are barracks and a food center with fast-food chains.

The wounded were dispersed among hospitals in central Texas, Cone said. Their identities, and the identities of the dead, were not immediately released.

Amber Bahr, 19, was shot in the stomach but was in stable condition, said her mother, Lisa Pfund of Random Lake, Wis.

"We know nothing, just that she was shot in the belly," Pfund said.

The Rev. Greg Schannep was about to head into a graduation ceremony when a man in uniform approached him, warning him that someone had opened fire. Schannep heard three volleys of gunfire and saw people running.

"There was a burst of shots and more bursts of shots and people running everywhere," said Schannep, who works for local Congressman John Carter.

The uniformed man who had warned him ran to the theater. Schannep said he could see the man's back was bloodied from a wound. The man survived, was treated and will be fine, Schannep said.

WALTER REED

Hasan graduated from Virginia Tech in 1997 and earned a doctorate in psychiatry from the Uniformed Services University of the Health Sciences in Bethesda, Md. He spent at least six years at Walter Reed before moving to Fort Hood.

He had been a "very devout" worshipper at the Muslim Community Center in Silver Spring, Md., attending prayers at least once a day, often in his Army fatigues, said Faizul Khan, a former imam there.

"To know something like this happened, I don't know what got into his mind," Khan said. "There was nothing extremist in his questions. He never showed any frustration. He never showed any remorse or wish for vengeance on anybody."

A co-worker identified as Col. Terry Lee told Fox News that Hasan opposed the U.S. role in Iraq and Afghanistan and told others that "we should not be in the war in the first place." He said Hasan acknowledged that soldiers have a duty to follow the commander in chief's orders, but was hoping that President Obama would order a pullout from the conflicts.

"When things weren't going that way," Lee said, "he became more agitated, more frustrated with the conflicts over there."

Obama called the shooting "a horrific outburst of violence" and promised to "get answers to every single question about this horrible incident." He offered his prayers to the wounded and the families of those killed, calling them "men and women who have made the selfless and courageous decision to risk — and at times give — their lives to protect the rest of us."

"It's difficult enough when we lose these brave Americans in battles overseas," Obama said. "It is horrifying that they should come under fire at an Army base on American soil."

INTERNET POSTINGS

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, the AP reported, 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.

One of the officials said yesterday that federal search warrants were being drawn up to authorize the seizure of Hasan's computer.

The Council on American-Islamic Relations moved quickly to call the attack "cowardly." The advocacy group for American Muslims said it condemned the shooting "in the strongest terms possible."

"No political or religious ideology could ever excuse such wanton and indiscriminate violence," CAIR said. "The attack was particularly heinous in that it targeted the all-volunteer army that protects our nation."