I thought from the get-go he was schizophrenic. But then, I’m not a psychiatrist. The forensic psychiatrists seem to think he was, too, though:
Cho Likely Schizophrenic, Evidence Suggests
Link: http://abcnews.go.com/Health/VATech/story?id=3050483&page=1
Still, I don’t consider this conclusive because, as you said, the field of psychology is complicated and we really don’t know enough.
I agree. My brother was schizophrenic and I could see it in his eyes and the way he was talking. He sounded paranoid and tortured. In no way does that excuse what he did. My brother was tortured too, and he didn’t kill 32 other people when he killed himself.