As someone who has had personal experience with morbid depression, I know that the events at Virginia Tech can be overanalyzed.
Suicide, at its core, is a last, desperate attempt to stop the hopelessness and pain of depression. Some people just curl up in a ball and exist with the depression; others self-medicate the feelings away with alchohol or drugs. The lucky ones find a competent psychiatrist.
Public suicide, which is what Cho did, is an act of control. A depressed person feels he has no control over his life. In publicly killing himself he has proven his control of the only thing he has left to control - the place, time, and manner of his own death.
Mass murder with suicide is simply graffiti. Whether it happens on a campus or the streets of Baghdad, it is nothing more than painting "I was here!" on the walls with blood. There is no social-political reason beyond an invisible man proving to himself and the world that he exists.
The art is La Femme Qui Pleure by Picasso.