That's the picture beginning to emerge from discussions with those who knew him.
One professor says she even took Cho out of a class and tutored him herself, along with ringing an alarm bell for university officials, only to be told there was little that could be done.
And an ex-classmate told The Early Show Wednesday that Cho made her "nervous."
Va. Tech junior Sara Stevens, who is a former CBS News intern, explained to Smith that she "had classes with him for three years, and he was known as being expressionless. He usually sat in class and … I never heard him speak once in three years.
"I had no idea as to what his mental state was like. I had no idea as to what kind of personality he had, because he literally just sat in class and stared off into space."
That is, until a playwriting class Cho and Stevens were in.
There, she told Smith, Cho's writing was full of "very graphic things. He wrote a play about how his father — there was a character where the father raped the son and the son was gonna get back at him by killing him. And it became very brutal and graphic, and vulgar with the language. And there was another play about how he was gonna get revenge on a teacher who had given him low marks. And so he just, once again, lashed out within the play, with just very brutal, vulgar language. It was hard to read."
Stevens says others in the class didn't know how to take what he was producing.
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The reaction, she says, was "mixed. A lot of us, because the language was so graphic and we didn't have any indication as to what his personality was like, took it as perhaps he was joking and this was meant to be taken as a comedy and, you know, because it was just so over the top that, you know, how could this be taken seriously?
"But it brushed me in the wrong way and it was hard for me to read and I told him that in class. Literally, he made me so nervous, is the only thing I could give him as a remark was that I thought his language was too graphic."
Stevens added that the students were supposed to critique each others' work in e-mails before classes, but Cho never took part in that exercise.
She says she found Cho's behavior "disconcerting. … I just worried for what his well-being was. And he just — he was a question mark, essentially."
Some former classmates called Cho the "Question Mark Kid" because he used one on a sign-in sheet for a class.
And it wasn't just his fellow students whose antennae were raised by Cho.
The former chairman of the Virginia Tech English department, and current Alumni Distinguished Professor of English, told Smith Wednesday she had to intervene when Cho raised eyebrows.
Lucinda Roy says, at one point, she saw some poetry that he'd written, and it "seemed to be very angry. And the, when I questioned him about it — he was in somebody else's class, and that faculty member came to me as chair of the department — and I just asked him about it, and he wrote me a very long, rambling, angry e-mail, just very arrogant, and seemingly dismissive of his faculty member. And so I called him in to talk with him to find out what was going on."
Roy says she decided to tutor Cho personally, because she "didn't feel that the students felt safe. They expressed to their faculty member some discomfort. And she said that she wasn't comfortable teaching him anymore. And unfortunately, when I checked with counseling and the Virginia Tech police and student affairs and so on, the only option I had was to put him in another class. And I couldn't do that. So I decided I'd take him myself."
The university officials she approached "were very concerned," Roy says. "And their response was immediate, in terms of trying to help. And then, they seemed to hit a wall where there are all these legal issues. Unless he'd issued an actual threat, I was told, he had never said he was going to do harm to himself or someone else in an explicit way. But, the case I tried to make as best I could was that there was an underlying threat in what he was doing. And that, clearly, this was a very disturbed young man."
Roy says she kept urging Cho to seem help from school counselors, and he claimed at one point to have gotten some, though she couldn't confirm that.
Dealing with him was "very strange," Roy says. "If you were to say something to him, it would take him about 10 to 20 seconds to say anything back. So there would be a long, long pause. And then, when he did speak, he spoke only in a whisper. So, you'd have to lean in to hear what he was saying. And he always wore sunglasses inside, so you couldn't see his face. And a hat. And it was only, as we worked together a little bit, I was able to ask him to take his sunglasses off, and he did that, in the end."
The aftermath of the shootings has been "more painful than I think anyone can imagine. But, my pain still is dwarfed by the pain and the grief of the parents. And so, always, we must bear that in mind. And we just have to be strong and help each other and love each other."
Sentiments echoed by Stevens, who told Smith her reaction was: "I guess, just like any other student. Um, there's, you know, that initial guilt with, 'Oh, my god, I've lost friends and my friends have lost friends, and I knew the person who caused that. I knew that person who took their lives away.' And, you know, to deal with that is hard, especially when I saw signs in the class.
"But, you know, the faculty and my professor from that class have reached out and told us that there's a difference between violent writing and violent behavior. And that, you know, sometimes writing serves as a form of catharsis, and there's no way we could have known and so, now it's just that hurt dealing with."