Eric Harris and Dylan Klebold were two students who committed the Columbine High School massacre. They fatally shot 13 students together, then fatally shot themselves. A possible cause of the shooting is the bullying and rejection Eric and Dylan received from classmates. Eric Harris was involuntarily not getting laid
Incel Wiki does not support or condone the Columbine murders.
Sexual Frustration and incelibacy
Dylan and Eric were very likely bullied (like every male who is bullied) due to sexual reasons as male bullies usually bully to keep other men from having sex or intimacy. Eric Harris e.g. experienced a great deal of rejection by women, once writing up women who rejected him in a list of people who he thought, "should have died". Eric most likely died a virgin according to careful analysis of his life.
“”If people would give me more compliments all of this [the attack] might still be avoidable.... You know what, maybe I just need to get laid. Maybe that'll just change some s--- around."
The quote above suggests Eric felt the attack would have been avoidable if he could just, "get laid".
In his last journal entry, Eric Harris lamented the fact that he couldn't "fuck", suggesting having sex was a top priority for him, and complained about not getting any despite being nice and considerate.
“”Right now I'm trying to get fucked and trying to finish off these time bombs. NBK came quick. why the fuck cant I get any? I mean, I'm nice and considerate and all that shit, but nooooo. I think I try to hard. but I kinda need to considering NBK is closing in."
Researchers, led by Daniel Provenzano from the University of Windsor in Canada, found that bullying probably evolved as a behavior for men to show their strength and assert dominance, while signaling to women that they are good prospective mates who will provide for their needs and offspring. Professionals dealing with young adults need to recognize the role of sexual motivation in bullying, suggests Provenzano. 
Eric Harris made Doom levels.