The graphic videotape and sadistic snapshots only reinforce what investigators already knew. Virginia Tech killer Seung-Hui Cho was a deranged loner, intent on exacting revenge for his own feelings of isolation. But sources say Cho's hate-filled manifesto has provided little useful evidence in a rambling diatribe sent to NBC news. Cho sought to justify his plans for mass murder ("You forced me into a corner, and gave me only one option"), blaming everyone but himself for the killing spree. Today investigators criticized the media for broadcasting images, which they say glorified Cho and inflicted new pain on those already shattered by his rampage.

That we are rather disappointed in the editorial decision to broadcast these disturbing images.

Many on this campus still reeling for Monday's slaughter agree, saying they've now been victimized twice.

He put that video out there so everyone can see it. And it means we are doing his wishes which I don't agree with at all.

Investigators say Cho had been planning his murder spree for at least two months. And time-date stamps on images from Cho's computer and digital camera should help them further refine the timeline. It is clear looking at the backgrounds, Cho recorded his ramblings at various times in at least 3 separate places, his dorm room, inside a rental car, and from an undefined location. But sources say the pictures also raise questions, did Cho have help? Did someone else take the pictures or have any knowledge of his plans? A preliminary analysis suggested Cho took the pictures himself. But FBI photo experts are still studying details. And criminal profilers are taking apart Cho's statements word by word, trying better to understand the mind of the man behind the guns.

The way he talks on the tape, the disjointed manner he talks, the sort of delusions of grandeur, those things are symptoms of, of mental illness, and that we don't, as far as I know, was not treated.

Finally, investigators are also looking for any clues as to what set Cho off. His rampage came just days short of tomorrow's anniversary of the Columbine massacre. And in his tape, Cho praises the Columbine killers. And there is a question whether the Korean-born Cho drew any inspiration from an ultra-violent Korean-made film called "old boy". Two of Cho's photos, one with a hammer, the other with a gun closely mirror promotional shots for the movie.

The release of Cho's graphic images has set off a predictable wave of would-be copycats and hoaxes. A number of schools around the country have received threats, and already at least one student has been arrested for carrying a loaded gun to a high school near Seattle. Bob Orr, CBS News. Blacksburg, Virginia.