Two Connecticut teenagers were arrested and may be expelled from their high school after allegedly making threats to their peers while wearing Columbine costumes on Halloween.

A teenager at Radnor High School outside of Philadelphia, Pa. was arrested on Monday for allegedly formulating a plot to become the "first female mass murder." She had reportedly written extensive notes on how to murder her classmates and teacher before a pep rally.

Oregon teenager Grant Acord will be charged with attempted aggravated murder after he was found with six bombs in his bedroom, which he allegedly planned to use on an attack on his school.

Here's something that almost all the mass killers of the last fifteen years or so have in common: they've been called "nerds." James Holmes, who allegedly murdered 12 people in a crowded Colorado movie theater on Friday morning, was described as a "nerd" by his uncle within hours of the shooting. Norwegian mass murderer Anders Behring Breivik is, in the Telegraph, a "puffy-faced computer game nerd." Columbine killers Eric Harris and Dylan Klebold were "innocuous nerds," the Los Angeles Times claimed in 1999.

The 1999 edition of Rebelations, the yearbook for Columbine High, is fetching bids right now on an online memorabilia auction site. Yes, you can own the yearbook that features murderers and their victims for $500. [Update: The item has been withdrawn. See below.]

Fighting a fire at Denver's Southwest Plaza Mall, about two miles from Columbine High, firefighters discovered two tanks of propane and a homemade pipe bomb stored in the food court. Nothing had detonated and no one was injured, yet the implications are downright chilling.

An adult male is in custody after shooting two people at a middle school in Littleton, Colorado. The victims, a boy and a girl, are in a local hospital, and neither injury "appears to be life-threatening," according to local authorities.