In the morning, he went to the corner shop where he lived near Fort Hood to buy coffee. Security video shows him exchanging chit-chat and smiling. In the afternoon, he went to a squat building inside the military facility filled with fellow soldiers preparing to deploy. He pulled out two handguns, and yelled "Allahu Akbar" – God is great! – and he opened fire. The carnage was quick and terrible: 13 lay dead or dying; 30 more were wounded.

For a few hours late on Thursday, it seemed this would follow the usual sad script of shooting tragedies in America. The "monster" assailant would turn the weapon on himself or be instantly gunned down by others. But Nidal Malik Hasan, an Army psychiatrist with the rank of major, survived. Felled on the scene by bullets fired by a civilian police officer, he was last night in a stable condition on a respirator.

So there will be no quick dispatching of 39-year-old Hasan, raised in Virginia to Palestinian immigrant parents, into the darker corners of US history. Though not yet well enough to be interviewed, he may one day provide answers to questions that for now seem impossible. What short-circuit occurred in his brain that brought him to this, and when? What were these killings for? Yes, pieces of his past speak of a conflicted and disgruntled soul. He was serious and a loner. That fits the profile. But who saw anything to suggest a capacity to commit evil on this scale? His one-man rampage, committed after the lunch-hour at the Soldier Readiness Centre on the largest military base in the world – the young men and women were queuing up for medical shots for Iraq and Afghanistan, no doubt contemplating the perils that lay ahead – plunged a nation into shock.

It would be most convenient to describe what happened as another terrorist attack on America. As the investigation into the shootings got off the ground, the search for any possible links between Hasan and overseas or domestic terror groups is certain to intensify. There is no early evidence of any such ties.

Suicide bombers

Nevertheless, reports quickly surfaced that Hasan had come to the attention of counter-terror officers six months ago because of a posting on a website where someone with the same name favourably compared a soldier who throws himself on a grenade to protect his comrades with Islamist suicide bombers. It was the kind of post that always sets off alarm bells if they are spotted.

"If one suicide bomber can kill 100 enemy soldiers because they were caught off guard that would be considered a strategic victory," the man wrote. It has not yet been confirmed that the two Hasans were the same.

A broader portrait was becoming visible. One of three siblings born in Arlington, Virginia, Nidal Hasan joined the army as a teen straight out of high school. (It was a choice his parents, both of whom are now dead, disapproved of.) He made a familiar kind of deal: if the army paid for his higher education, he would serve in its ranks for a determined number of years thereafter. He won a bachelors degree at Virginia Tech – the scene, as it happens, of America's worst-ever killing spree in 2007 when a lone gunmen massacred 32 – and then went on to train in medicine and psychiatry at a military teaching hospital in Bethesda, Maryland, outside Washington.

From there, Hasan was transferred to the biggest and most important of America's veterans' hospitals, the Walter Reed Medical Centre in Washington, where he remained for six years first as an intern then finally as a full partner helping a team of psychiatrists treat soldiers.

The suffering he witnessed – he spoke to one family member of a patient who was so badly burned it was as if his skin had melted from his face – would tax anyone's emotions. By the time Major Hasan reported for duty at Fort Hood in July this year, several things had apparently come together in his head. He wanted out of the military. He disapproved of the missions in Iraq and in Afghanistan. He was disappointed that Barack Obama was stepping up engagement in the latter. Under no circumstances was he ready to be deployed himself.

That he may have been troubled while at Walter Reed is not a surprise to some who knew him. At a community mosque in Silver Spring, he mostly kept to himself, but did enrol in a dating service there. "He came to the mosque one or two times to see if there were any suitable girls to marry," said Faizul Khan, a former Imam there. "I don't think he ever had a match... he had too many conditions."

A former superior officer at Walter Reed, meanwhile, acknowledged anonymously that issues with Major Hasan's performance in the psychiatry unit had arisen in his years there, and that he had been put under special supervision. He had also been heard voicing his misgivings about the war in Iraq and getting into arguments with fellow soldiers, which carried on at Fort Hood.

Retired Army Colonel Terry Lee told Fox News he had worked with Hasan, who apparently had been "hoping that President Obama would pull troops out". He added: "When things weren't going that way, he became more agitated, more frustrated with the conflicts over there. He made his views well known about how he felt about the US involvement in Iraq and Afghanistan."

So there were pressures simmering somewhere in Hasan. An aunt, Noel Hasan, told the Washington Post that after 9/11, her nephew had endured taunting inside the army because of his religion. It had started to wear him down. "I know what that is like," she said. "Some people can take it, some cannot. He wanted out of the military, and they would not let him leave, even after he offered to repay" for his training.

Apparently the avenues to leaving the army were nonetheless all blocked to Hasan. At Fort Hood he was assigned duties similar to those at Walter Reed, once more looking after stressed soldiers returning from war zones.

Muslim faith

In the summer, meanwhile, Hasan had a run-in with another soldier to do with his Muslim faith. The latter allegedly ripped a sticker from Hasan's car that said 'Allah is Love' and scratched it with a key causing $1,000 in damage. The case was referred for prosecution.

His stress was to spike, however, when he learnt his time had come to go overseas. "He was doing everything he could to avoid that," a cousin in Virginia, Nader Hasan, told The New York Times. "He wanted to do whatever he could within the rules to make sure he wouldn't go over." According to reports, the orders had already been given. Major Hasan, a very reluctant warrior, was bound for Afghanistan.

Just last Wednesday, the man who was later caught smiling in the grocery shop, was knocking on the door of his neighbour, Patricia Villa, in the off-base apartment complex where he lived, offering her spinach from his freezer. The reason: his deployment orders had come. His landlord, Jose Padilla, said he refused to take his deposit and last month's rent cheque back, asking that the $400 should go to someone who "needed it".

Hasan knew his days in that apartment were over. Perhaps those gestures indicate that he also knew his impending departure from his small home had little to do with Afghanistan – and was instead the first step on a path he was about to take into the pages of America's lengthening book of mass-murdering infamy.

Hasan's praise for suicide bombers

Well before Thursday's attack, the FBI had become aware of a web user with the login NidalHasan. He posted the following message to the website Scribd on 20 July:

There was a grenade thrown amongst a group of American soldiers. One of the soldiers, feeling that it was too late for everyone to flee, jumped on the grave with the intention of saving his comrades. Indeed he saved them. He intentionally took his life for a noble cause i.e. saving the lives of his soldiers. To say that this soldier committed suicide is inappropriate. It's more appropriate to say he is a brave hero that sacrificed his life for a more noble cause. Scholars have paralleled this to suicide bombers whose intention, by sacrificing their lives, is to help save Muslims by killing enemy soldiers. If one suicide bomber can kill 100 enemy soldiers because they were caught off guard that would be considered a strategic victory. Their intention is not to die because of some despair. The same can be said for the kamikazees in Japan. They died to kill the enemies for the homeland. You can call them crazy if you want, but their act was not one of suicide that is despised by Islam. So the scholars' main point is that "IT SEEMS AS THOUGH YOUR INTENTION IS THE MAIN ISSUE" and Allah knows best.