Harris and Klebold "laughed at petty school shooters," Cullen reports. They sought murder on a grander scale. They planned first to set off bombs in the school cafeteria to kill perhaps 600. Then they would shoot the survivors as they fled. Then their cars, laden with still more bombs, would explode amid the crowd of rescue workers and parents rushing to the school. It all might have come off if they had not miswired the timers on the propane bombs in the cafeteria.
What motivated them? Here, Cullen says, it is necessary to distinguish Klebold from Harris. Klebold was a depressed and troubled kid who could have been saved. Harris was an icy killer. He once thought about hijacking a plane and flying it into Manhattan.
You wrote:"Those who are lost without purpose are much more likely to act out in some inappropriate manner. Here, they acted out in suicidal rage."
I believe Klebold might have been salvageable if the culture had not degenerated so far from traditional values. Harris sounds like a psychopath that was determined to go out in a murderous blaze of infamy, i.e. he was beyond help or hope.
Or a rage driven soul, trying to outdo the other rage driven kids. What you quote strongly suggests that he wanted his angry statement to far outdo the younger kids in Paducah. Was he a natural sociopath--there are such--or reacting with fury to a sense that something (something that he couldn't even define) was missing from his life. I would lean towards the latter, because most sociopaths do not commit suicide, but demonstrate their pathology over much longer time frames. The misery they cause others may be a game, but not one that requires immediate self-destruction, where there is not much time for personal enjoyment.
William Flax