'You have vandalised my heart, raped my soul and torched my conscience'
Part One: The Killer

The question mark kid. The boy who didn't talk in class. The weirdo loner. These are the names by which Cho Seung-Hui was known. He was a cypher. He stood for nothing. A lost, empty young man, filled with ego and anger and little else. In the last days of his life, he tried to fill the void that he'd become by morphing into something akin to the character Travis Bickle in the film Taxi Driver. He assumed the identity of an avenging angel and even gave his new persona a name: Ismail Ax.

When his corpse was discovered after his mass murder of 32 innocent men and women at Virginia Tech University, which was followed by his suicide, the words "Ismail Ax" were found written on his arm. He used the same name when he posted his "murder manifesto" to NBC Television. What does it mean? No-one knows for sure. But it could well be a reference to Ishmael, son of the prophet Abraham in the Book of Genesis. Ishmael was a man rejected by family, friends and society. The first book of the Bible says of Ishmael: "His hand will be against everyone and everyone's hand against him, and he will live in hostility toward all his brothers." Ishmael, like Cho, can be seen as nothing more than an empty symbol of anger and violence.

Others knew him at the Question Mark Kid. On the first day of one class, students were asked to stand up and introduce themselves by name. Cho stayed seated and muttered that his name was "Question Mark".

Steven Davis, who was in drama class with Cho, added: "Nobody took too much notice of him except for that's the kinda weird quiet kid who never talks'. Until we read his work. And then it was like, Whoa, something is off.'"

On the outside, Cho was a silent, isolated young man. Other students describe him wandering around campus like a "ghost". But inside, he was changing. For 23 years, he'd been a nobody: at first a friendless kid, then a friendless adult. But his writing revealed a desire for violence spurred by a sense of powerlessness and rage against authority. His revenge fantasies were growing and finding a voice. In one short play, which he wrote for his creative writing course - a brief, badly written drama called Richard McBeef - he describes an adolescent boy's rage against his step-father. The work is clumsy and confused and riddled with the most brutal and crude expletives. It ends with the father figure moving to kill the boy.

In Mr Brownstone, another of Cho's plays - equally poorly executed and equally filled with foul language and howling rage - a group of high school kids obsessively talk about their hatred for their teacher. They describe repeatedly the sense of being "raped" - metaphorically - by the teacher. In the video clips and 1800-word rant that Cho sent to the media in the midst of his killings, he talks about the sense of his soul being raped by his unnamed tormentors.

Not long before the killings, Cho had been what US teenagers would have described as "nerdy looking". He had unstyled hair, glasses and a fairly slight body frame. That changed. He started pumping iron and bulked up, ditched the glasses, cropped his hair into a severe buzz cut and bought military-style clothes. He also bought guns and ammo - more than enough to kill 32 victims and then take his own life.

Cho, a South Korean immigrant who moved to the US aged eight, was the child of impoverished parents. He seemed, from his murder manifesto, to be motivated by hatred of the rich kids who he felt had rejected and mocked him. "You had everything you wanted," he says. "Your Mercedes wasn't enough, you brats. Your golden necklaces weren't enough, you snobs. Your trust fund wasn't enough. Your vodka and cognac weren't enough. All your debaucheries weren't enough. Those weren't enough to fulfil your hedonistic needs. You had everything.

"You have vandalised my heart, raped my soul and torched my conscience. You thought it was one pathetic boy's life you were extinguishing. Thanks to you, I die like Jesus Christ, to inspire generations of the weak and the defenceless people. Do you know what it feels like to be humiliated and be impaled upon on a cross? And left to bleed to death for your amusement? You have never felt a single ounce of pain your whole life. I didn't have to do this. I could have left. I could have fled. But no, I will no longer run. When the time came, I did it. I had to. This is it. This is where it all ends. End of the road. What a life it was. Some life."

It was indeed "some life". Cho's extended family in South Korea say that he was diagnosed as autistic not long after his parents arrived in the US to work in a laundry. Some family members even feared he was mute. His great-aunt, Kim Yang-Sun, said: "He was very quiet and only followed his mother and father around and when others called his name he just answered yes' or no' but never showed any feelings or emotions."

Cho's uncle, Chan Kim, said: "Both his parents knew he had mental problems but they were poor and they couldn't send him to a special hospital His parents worked and did not have time to look after his condition and didn't give him special treatment."

A clear picture of young Cho's family life hasn't yet emerged. But Cho may have faded in the shadow of his high-achieving sister, Cho Sun-Kyung, a Princeton graduate who now works as a contractor for the US state department. It was Sun-Kyung who expressed grief for the friends and relatives of her brother's victims in a statement from the Cho family.

When the boy arrived in Virginia with his family, he found himself an outsider with obvious developmental difficulties in the bear-pit of US high school life. In a world where children are expected to possess beauty, sporting prowess, hosts of friends, wit and wisdom, Cho was a victim. In his murder manifesto, he referred to the two Columbine killers - also social misfits - as "martyrs".

Cho had difficulty making himself understood verbally. Perhaps his autism exacerbated the problems any foreigner would have mastering English in the US education system. Cho almost never spoke in class. When he did, his peers would jeer "go back to China".

In English class at his high school in Chantilly, Virginia, Cho just stared at the floor when the teacher asked him to read aloud. When threatened with a failing grade for refusing to participate, Cho spoke in a strange, deep voice. Chris Davids, who went to the same school and university as Cho, said: "It sounded like he had something in his mouth. The class started laughing and pointing."

Another high school contemporary, Stephanie Roberts, recalled: "I remember him as a shy kid who didn't really want to talk to anybody There were just some people who were really mean to him, and they would push him down and laugh at him. He didn't speak English really well, and they would really make fun of him."

Regan Wilder, who also went to school and university with Cho, said he walked with his head held down, and seldom spoke. On the few occasions that Cho did speak, it was in a "real low mutter, like a whisper".

Wilder said teachers tried to encourage him to take part in lessons but "he would only shrug his shoulders or he'd give like two-word responses, and I think it just got to the point where teachers just gave up because they realised he wasn't going to come out of the shell he was in, so they just kind of passed him over for the most part as time went on".

Little changed when Cho got to university. At Virginia Tech, said Wilder, Cho "always had that same damn blank stare, like a glare, on his face. And I'd always try to make eye contact with him because I recognised the kid because I'd seen him for six years, but he'd always just look right past you like you weren't there."

Karan Grewal, one of Cho's roommates at Virginia Tech, said: "I tried to be friends with him, but after multiple attempts where he showed no interest, I thought he just wanted to be lonely. He never showed anger on his face. Whenever I tried to talk to him, he would just sit there and ignore me as if I was invisible. He just sat there staring through space most of the time he showed no emotion ever."

Cho ticked all the boxes for potential "school shooter". Lonely, bullied, vengeful, male. "In virtually every regard, Mr Cho is prototypical of mass killers that I've studied in the past 25 years," said Northeastern University criminal justice professor James Alan Fox.

A 2002 federal study of school shooters found that 71% "felt bullied, persecuted or injured by others prior to the attack". The study's co-author Marisa Randazzo, the former chief research psychologist at the US Secret Service, whose study was conducted jointly with the Education Department, said that Cho was almost "a poster child for the pattern that we saw". At least two of the victims of his shooting rampage attended the same high school as Cho.

Lots of kids are seen as "weirdos", but they don't find faculty staff reporting them to university administrators and police. Cho did. In autumn 2005, the poet Nikki Giovanni, a professor of creative writing at Virginia Tech's English faculty, refused to have Cho in her class because he was "intimidating" and frightened others. The then chair of the English department, Lucinda Roy, had to speak to Cho after allegations that he was taking so-called "up-skirt" pictures of girls under desks. Roy said his reaction was "very arrogant" and had an "underlying tone of anger". Nonetheless, Roy took Cho under her wing, teaching him in one-to-one sessions. She also put in place a system which would have alerted colleagues to any threatening behaviour from Cho - using a coded "red flag" word. Carolyn Rude, the current English department chair, said a number of "urgent reports" had been made about the student. Staff had also urged him to seek counselling.

In the winter of 2005, he was accused of stalking two women, and an associate alerted campus police that he might be suicidal. No charges were pressed but he was sent for psychological assessment and found to be "an imminent danger to himself". One doctor noted: "Affect is flat and mood is depressed. He denies suicidal ideations. He does not acknowledge symptoms of a thought disorder. His insight and judgement are sound." He was not committed to a mental hospital - if he had been, state law would have prevented him buying firearms - but sent for outpatient treatment instead.

By the autumn of 2006, Cho had written his two most violent and rambling short plays - Richard McBeef and Mr Brownstone. Other students were by now refusing to critique his work because it was so vulgar and violent. Eight teachers in the 18 months leading up the shooting set up a task force on how to deal with Cho. Students began to refuse to come to classes he was attending.

One Virginia Tech classmate tried to befriend Cho. Ross Alameddine and Cho sat together in a class which analysed horror literature and films. Cho shot Alameddine dead on Monday.

Cho stopped coming to classes in the weeks before the killings. During this period, he bought guns and military-style clothing. He hired a hotel room and rented a van where he could work in secret on his murder manifesto.

Then, on Monday morning, he arrived at the dorm room of Emily Hilscher - a pretty, popular, all-American girl - and shot her dead. He killed another student who'd come to help Hilscher, and then left to post his murder manifesto to the media. Two hours later, he began his rampage in earnest.

South Korea, stunned by the killings, is trying to anatomise what went wrong with Cho. One newspaper worried that immigrants to the US were so busy making money that they loose touch with their children.

Perhaps, the one man who is closest to understanding the horror and sadness of the life, crimes and death of Cho Seung-Hui is Professor Clifford Randall, who lost a teaching friend and colleague in the murder spree. "CS Lewis," commented Randall, referring to the Ulster author and scholar, "said that evil is the absence of love. And the young man who did this had no sense of love in his life."