From the most definitive research on Columbine, Dave Cullen's book Columbine, via the article 7 Myths about Columbine:
Myth #3: The Columbine killers targeted certain kinds of students.We also heard, about Columbine, that those two mass shooters would have been stopped if someone had a gun. There were two armed cops who were unsuccessful in stopping those two shooters. Likewise, there was a security guard, and numerous armed students, mostly trained veterans, on the Oregon campus - it was NOT a gun free zone - and they did NOTHING to prevent the tragedy from taking place. In fact, no civilian with a gun has EVER prevented or stopped a mass shooting in the United States, even when on the scene.
Truth: Although initial news reports claimed the Columbine killers had targeted minorities, jocks, and Christians, the killing was indiscriminate. Their initial plan was to blow up hundreds of students in the cafeteria. When the bombs failed to go off, they killed students randomly. Interestingly enough, Eric’s friends described him as a sports enthusiast, and two of his best friends were Asian and African American.
Myth #6: Cassie Bernall was martyred for her faith in God.
Truth: According to the eyewitness under the table with her, Cassie was shot when Eric poked his shotgun under the table and said, “Peekaboo.” The 911 tape verifies this testimony.
The martyr story arose from the testimony from another student in the library, Craig Scott (brother to victim, Rachel Scott), who recounted a conversation that took place across the room. Valeen Schnurr was the one who actually professed her faith in God, and this took place after she was shot. As she lay bleeding, she prayed, “Oh my God, don’t let me die.” Dylan turned around and asked her, “God? Do you believe in God?” Valeen said, “Yes, I believe in God.” When the killer asked why, she replied, “Because it’s how my parents raised me.”