He seemed angry and depressed.
He wrote creepy things about death in his English class.
So how come no one flagged this guy as a problem before he gunned down 32 people?
To which I would respond: Are you serious?
Anyone who's ever been to college has run into dozens of kids who fit that description.
In fact, you can find quiet, angry, creepy, obsessed people in any workplace in the country.
But just because someone's a weirdo, it doesn't mean he's going to buy a couple of guns and start shooting people.
We keep waiting for science to develop a nice, reliable psychological profile of these mass murderers, something we can consult in a textbook and then look at a person and say with utter certainty: "OK, that guy over there. He's going to snap and shoot someone any minute. Let's put him away."
And that's never going to happen.
Common sense tells you that.
As does the fact that we'd be trampling all over our civil liberties if we start locking people up for being weirdos.
Still, Lucinda Roy, one of Cho Seung-Hui's teachers, was sufficiently disturbed by the vibe he gave off that she urged him to seek counseling.
A teacher he had two years ago, Nikki Giovanni, removed him from a poetry class, according to The Washington Post, because his writing was "sinister" and was freaking out his fellow students.
Giovanni warned Roy about the young man's behavior.
And Roy says she alerted the university's administrators.
But what could the school do at that point?
Cho hadn't made any threats - at least none that the school knew of.
He was just being, well, weird.
And writing weird stuff for his classes.
In this country, we don't put people away for that.
Still, now that more and more is being learned about Cho's dark side - there's the violent multi-media manifesto he'd mailed to NBC News, there's talk he might have set a fire in a dorm room, stalked women, called in bomb threats - the urge to come up with a foolproof template for identifying potential mass murderers is overwhelming.
Since the Columbine High shootings eight years ago, when two students killed 13 people and then turned their guns on themselves, we're leery of kids described as quiet loners and disaffected youths.
We're leery of kids said to be obsessed with violent video games.
Or kids who dress in long leather trench coats and shades, like a character out of The Matrix.
But how do you quantify these sorts of things to make them useful for identifying a potentially deranged gunman?
How quiet is too quiet before we raise a red flag?
How much of a loner do you have to be?
Does having one good friend who feels as alienated as you do make it less likely you'll pick up a gun and start shooting people?
And how obsessed with violent video games do you have to be to be considered a threat to society?
If a kid plays them a dozen times a day, is that a sign he's about to go off?
How about if he plays them a dozen times a week?
All I know is, the howlers on the cable and radio talk shows yesterday didn't have the answers.
That's because there are no answers.