School shooters tend to act impulsively and attack the targets of their rage: students and faculty. But Harris and Klebold planned for a year and dreamed much bigger. The school served as means to a grander end, to terrorize the entire nation by attacking a symbol of American life. Their slaughter was aimed at students and teachers, but it was not motivated by resentment of them in particular. Students and teachers were just convenient quarry, what Timothy McVeigh described as “collateral damage.”
The killers, in fact, laughed at petty school shooters. They bragged about dwarfing the carnage of the Oklahoma City bombing and originally scheduled their bloody performance for its anniversary. Klebold boasted on video about inflicting “the most deaths in U.S. history.” Columbine was intended not primarily as a shooting at all, but as a bombing on a massive scale. If they hadn’t been so bad at wiring the timers, the propane bombs they set in the cafeteria would have wiped out 600 people. After those bombs went off, they planned to gun down fleeing survivors. An explosive third act would follow, when their cars, packed with still more bombs, would rip through still more crowds, presumably of survivors, rescue workers, and reporters. The climax would be captured on live television. It wasn’t just “fame” they were after
"At last we know why the Columbine killers did it."