Cho Seung-Hui was the 23-year-old English major who calmly and methodically gunned down 32 students and faculty members at Virginia Tech last week before killing himself, leaving the campus and the country stunned and sorrowful. Along with the grief have come questions about what, if anything, could have been done to prevent Cho's rampage. Some have concluded that the university ignored obvious warning signs and failed to protect the community from a deeply disturbed and violent student. They point to events that, in retrospect, appear to be enormous red flags, signaling an inevitable catastrophe. However, such criticisms tend to ignore a more complex reality. For instance, how do you help a student who doesn't want to be helped? What is the line between depressed and dangerous? When does an eccentric loner become a potential killer? Those are the tough calls that colleges make all the time. And, as the tragedy at Virginia Tech proves, the stakes couldn't be higher. [This article was reported by Elyse Ashburn, Thomas Bartlett, Scott Carlson, Josh Fischman, John Gravois, Eric Hoover, Sara Lipka, and Martin Van Der Werf and written by Mr. Bartlett.]