Girl in Colo. School Shooting Plot Charged as Adult She planned to make assault deadly as possible: prosecutors By Arden Dier, Newser Staff Posted Jan 6, 2016 2:02 PM CST 77 comments Comments This photo shows Mountain Vista High School, the suburban Denver high school, in Highlands Ranch, Colo. (AP Photo/Brennan Linsley) (Newser) – One of two suspects accused of plotting to kill classmates and teachers at a suburban Denver high school has been charged as an adult. Sienna Johnson, 16, faces felony charges of conspiracy to commit first-degree murder related to a shooting plot that police tell the Denver Post was to "inflict as much damage as possible" on Mountain Vista High School in the days before Christmas. Prosecutors allege Johnson and a female accomplice—whose case remains in juvenile court—made maps of the building that noted the location of certain people, including deputies assigned to the school. Authorities say Johnson also tried to get a weapon, referenced school shootings, posted violent images on Tumblr, and mentioned the movie Natural Born Killers—also referenced by the Columbine shooters—in her journal, per 9News. The plot was uncovered thanks to an anonymous tip, police say. Johnson was ordered held on a $1 million bail during a hearing Tuesday. "We still feel she is a danger to the community," a deputy DA says. Authorities say Johnson told them she would ramp up her plans for mass murder after her release and was "faking her mental progress" at a hospital following her arrest. They also say she was using a BB gun for target practice and had a history of hurting pets. Johnson's lawyer says the claims are "grossly exaggerated" and will attempt to move her case back to juvenile court at a March 30 hearing. Prosecutors will review a psychiatric evaluation before deciding whether to charge Johnson's alleged conspirator as an adult. The girl's attorney notes "there is no direct evidence ... of [the] defendant's possession of any weapons, bombs, or incendiary devices. Instead, the prosecution's theory hinges upon entries written in [the] defendant's personal journal, which was seized by law enforcement without a warrant."