But police and university officials offered no clues as to exactly what set off Cho Seung-Hui, a 23-year-old senior, on the deadliest shooting rampage in modern U.S. history.
"He was a loner, and we're having difficulty finding information about him," school spokesman Larry Hincker said.
The emerging portrait of Cho, the quiet loner whose writing sent out alarms, is one that fits almost to a "T" a U.S. Secret Service profile of the, reports CBS News correspondent Wyatt Andrews.
In a study done after the Columbine massacre, the Secret Service studied 37 school shootings to learn the patterns of the school-aged assassins.
Most school attacks, the report said, come from loners with some kind of grievance, adds Andrews. "Many attackers felt bullied," ...or persecuted by others....and "more than half had revenge as a motive."
AOL News published two disturbing scripts Wednesday allegedly written by Cho for a Virginia Tech playwriting class last fall. Ian MacFarlane, a classmate of Cho's who now works for AOL, released the plays.
In one of Cho's plays, titled "Richard McBeef," the main character named "John" is alone in his room throwing darts at a target covered with a picture of his stepfather, the title character. John says: "I hate him. Must kill Dick. Must kill Dick. Dick must die. Kill Dick."
Classmates say that on the first day of a British literature class last year, students took turns introducing themsleves. When it was Cho Seung-Hui's turn to speak, he said nothing.
Click here for an interactive gallery of the victims.
The professor then looked at the sign-in sheet, and noticed that Cho had written a question mark instead of his name. The professor asked, "Is your name 'Question mark?"' A classmate, Julie Poole, says Cho offered little response.
She says he then spent much of the class sitting in the back of the room, wearing a hat and seldom participating.
Poole says, "We just really knew him as the question mark kid."
News reports said that Cho may have been taking medication for depression, that he was becoming increasingly violent and erratic, and that he left a note in his dorm in which he railed against "rich kids," "debauchery" and "deceitful charlatans" on campus.
In an interview with the New York Times, Joe Aust, a sophomore and Cho's roommate, described Cho as a quiet loner who was unknown to him.
"He was my roommate," Joe Aust, 19, told the Times. "I didn't know him that well, though."
He added: "He was always really, really quiet and kind of weird, keeping to himself all the time," he said. "I tried to make conversation with him in August or so and he would just give one word answers and not try and carry on the conversation."
Cho arrived in the United States as boy from South Korea in 1992 and was raised in suburban Washington, D.C., officials said. He was living on campus in a different dorm from the one where Monday's bloodbath began.
Professor Carolyn Rude, chairwoman of the university's English department, said she did not personally know the gunman. But she said she spoke with Lucinda Roy, the department's director of creative writing, who had Cho in one of her classes and described him as "troubled."
"There was some concern about him," Rude said. "Sometimes, in creative writing, people reveal things and you never know if it's creative or if they're describing things, if they're imagining things or just how real it might be. But we're all alert to not ignore things like this."
She said Cho was referred to the counseling service, but she said she did not know when, or what the outcome was. Rude refused to release any of his writings or his grades, citing privacy laws.
Receipts found in Cho's backpack allowed authorities to trace one of the two handguns used in the shootings, though the serial numbers for both weapons were wiped clean, CBS News reports. Cho carried a 9 mm handgun and a 22 mm handgun during the shootings, police said.
One of the guns used in the massacre, the 9 mm semi-automatic Glock 19, was purchased brand new at a Roanoke, Va. gun shop, Roanoke Firearms, 36 days ago, CBS News has learned.
According to store owner John Markell,for the gun and a box of 50 rounds of ammunition used primarily for target practice.
Markell says Cho was a "nice, clean-cut college kid." He says he had no suspicions about Cho's purchase, but that it's "just terrible" to learn what the gun was used for.