Ariz. teen accused of threating to kill people at school PHOENIX Authorities say a 16-year-old girl from Mesa was arrested Thursday after she posted a threat on YouTube that she had a plan to kill people at her high school and then commit suicide. CBS affiliate KPHO Phoenix reported that the person made the threat on a transgender YouTube channel, according to the Maricopa County Sheriff Office. The posting included: "I now literally have a plan of seriously hurting ... killing ... murdering people in my highschool. And a playlist to do it. The sheriff's office says the girl had access to guns at her home, but never brought firearms to Red Mountain High School in Mesa. The agency says investigators arrested the girl at her home Thursday morning and that she admitted to posting the threat. Red Mountain High School was in session Thursday. Investigators in Arizona say they received a tip about the girl from Canadian police.