Girl, 16, Charged as Adult with Conspiracy to Commit Murder After Plotting Attack on Denver-Area School

One of two teens accused of planning a deadly attack on her suburban Denver high school has been charged as an adult because, prosecutors say, she bought a BB gun for target practice and mapped detailed plans for an attack. Prosecutors charged 16-year-old Sienna Johnson with conspiracy to commit murder on Tuesday and requested that the girl not be allowed to return to Mountain Vista High School in the affluent suburb of Highlands Ranch, Colorado.

Disturbing details emerged in court Tuesday afternoon when the decision to charge Johnson as an adult was announced. According to Denver7 reporter Jennifer Kovaleski, “Johnson showed little emotion but she cracked a few smiles at her lawyers.”

Prosecutors said Johnson had a detailed map of where everyone in the school would be and knew the school resource officer schedule. They added that Johnson already bought a BB gun to use for target practice. The prosecution called her extremely violent and said she harmed pets in the past.

Prosecutors alleged Johnson wrote about “NBK” in her journal, which stands for natural born killers and was an obsession of the Columbine shooters, and drew “disturbing” images there. They said Johnson hasn’t shown any remorse, and she told detectives that if she was free, she’d attempt to execute the plot again.

Police arrested the girls on Dec. 12 after they were alerted to their scheme via a “text-a-tip program” developed for schools.

Authorities say the two had planned their attack in the days before Christmas to inflict as much damage as possible.

Prosecutors will decide whether to charge the second girl as an adult after the results of a mental health exam and other evidence come in. According to authorities, the girls had taken “an unspecified, significant step in their plot.”

An attorney for the girl whose case is still in juvenile court filed a motion fighting a media request to unseal documents in the case and claiming investigatory misconduct.

“There is no direct evidence in this case of (the) defendant’s possession of any weapons, bombs or incendiary devices,” the motion said. “Instead, the prosecution’s theory hinges upon entries written in defendant’s personal journal, which was seized by law enforcement without a warrant and without consent.”

But Douglas County sheriff Tony Spurlock said, “I think the text message and the information we obtained through our investigation saved lives for sure given the severity of the situation.”