As such details of the Virginia Tech shooter's life come out, and experts pore over his twisted writings and his videotaped rant, it is becoming increasingly clear that Cho was almost a textbook case of a school shooter: a painfully awkward, picked-on young man who lashed out with methodical fury at a world he believed was out to get him.

"In virtually every regard, Cho is prototypical of mass killers that I've studied in the past 25 years," said Northeastern University criminal justice professor James Alan Fox, co-author of 16 books on crime. "That doesn't mean, however, that one could have predicted his rampage."

When criminologists and psychologists look at mass murders, Cho fits the themes they see repeatedly: a friendless figure, someone who has been bullied, someone who blames others and is bent on revenge, a careful planner, a male. And someone who sent up warning signs with his strange behavior long in advance.

Among other things, the 23-year-old South Korean immigrant was sent to a psychiatric hospital and pronounced an imminent danger to himself. He was accused of stalking two women and photographing female students in class with his cell phone. And his violence-filled writings were so disturbing he was removed from one class, and professors begged him to get counseling. He rarely looked anyone in the eye and did not even talk to his own roommates.

Cho, who killed 32 people and committed suicide at the Blacksburg campus Monday, cast himself in his video diatribe as a persecuted figure like Jesus Christ. Cho, who came to the U.S. at about age 8 in 1992 and whose parents worked at a dry cleaners in suburban Washington, also ranted against rich "brats" with Mercedes, gold necklaces, cognac and trust funds.

Classmates in Virginia, where Cho grew up, said he was teased and picked on, apparently because of shyness and his strange, mumbly way of speaking.

Once, in English class at Westfield High School in Chantilly, Va., when the teacher had the students read aloud, Cho looked down when it was his turn, said Chris Davids, a Virginia Tech senior and high school classmate. After the teacher threatened him with an F for participation, Cho began reading in a strange, deep voice that sounded "like he had something in his mouth," Davids said.

"The whole class started laughing and pointing and saying, 'Go back to China,'" Davids said.

Stephanie Roberts, 22, a classmate of Cho's at Westfield High, said she never witnessed anyone picking on Cho in high school. But she said friends of hers who went to middle school with him told her they recalled him getting bullied there.

"There were just some people who were really mean to him and they would push him down and laugh at him," Roberts said. "He didn't speak English really well and they would really make fun of him."

Cho's great aunt, who lives in South Korea, said that because he did not speak much as a child and after the family emigrated to the United States, doctors thought he may be autistic.

"Normally sons and mothers talk. There was none of that for them. He was very cold," Kim Yang-soon said in an interview. "When they went to the United States, they told them it was autism."

Neither school officials, who have his educational records, nor police who have his medical records, have mentioned such a diagnosis this week. Autistic individuals often have difficulty communicating, but such a diagnosis would not necessarily explain his violence.

Regan Wilder, 21, who attended Virginia Tech, high school and middle school with Cho, said she was sure Cho probably was picked on in middle school, but so was everyone else. And it didn't seem as if English was the problem for him, she said. If he didn't speak English well, there were several other Korean students he could have reached out to for friendship, but he didn't.

One expert who has worked with mentally disturbed young criminals suggested that Cho's actions probably had genetic causes.