Professor Saw Suspected Shooter as 'Troubled'

Cho immigrated to the United States at age 8 with his family in 1992 and lived in Centerville, Va., before attending Virginia Tech, where he was a senior studying English literature at the time of the rampage.

He lived on campus in Harper Hall, a short walk away from West Ambler Johnston Hall where the first two killings occurred.

"The only thing we know about him is that he was a loner," said Larry Hincker, associate vice president of university relations. "We're having difficulty finding information about him."

Professor Carolyn Rude, chair of the university's English department, told NBC that she had spoken with one of Cho's creative writing professors who had described him as "troubled."

"There was some concern about him," Rude was quoted as saying. "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."

At a press conference the day after the shootings, Virginia Tech police chief Wendell Flinchum said it was "reasonable to assume that Cho was the shooter" in both incidents, but the police did not have evidence to confirm that at the time.

According to a spokesman with U.S. Citizenship and Immigration Services, Cho was a resident alien and held a green card, which allowed him to live and work indefinitely in the United States, although he could not vote or own a U.S. passport.

Neighbors of the Cho family in Centerville described the son as a "very quiet" boy who spent his free time playing basketball.

South Korean officials expressed their regret for the shootings and said they hoped the incident would not "stir up racial prejudice or confrontation" toward other South Koreans. Cho Byung-se (no relation), an administrator from the country's Foreign Ministry, said, "We are in shock beyond description. We convey deep condolences to victims, families and the American people."