According to police documents, Bookey attacked her brother's girlfriend, in the girl's bedroom, by first trying to suffocate her. She is then alleged to have smashed two bowls on the victim's head, and finally cut her throat with a shard from one of the bowls.
After she slit her brother's girlfriend's throat, Bookey called the St Croix County Sheriff's Department on 27 July, claiming that two men in a green pickup truck attempted to kidnap her while she was out for a bike ride.
She then claimed that she told the kidnappers that her brother's girlfriend was home alone and they should take her instead.
The Police arrived at the house and found the girlfriend in her bedroom, bleeding profusely. The girl, 15, was then taken by ambulance to a hospital.
Fortunately she survived the incident and told the Police that during the attack, Bookey asked her if she wanted to die or bleed out, with the 15-year-old opting for the latter.
Bookey told the victim that she was a 'crazy psychopath' looking for her first kill, then after she slit her throat, told her to "have a nice afterlife" and left the trailer.
Police investigators say that Bookey admitted she hated the 15-year-old because she made her brother happier than she was able to, and planned the attack a week and a half before, during previous bike rides.
Bookey confessed to the Police that on the day of the attack, she had left her home at around 4am and rode 11 miles on her bike to her victim's trailer, stating that she wanted to scare her brother's boyfriend so that her brother would "come back to the family" because he was so in love with the girlfriend.
Bookey's mother, Dawn Bookey, told the Associated Press she had no idea about the planned assault.
"We had no clue," the mother said. "There were no signs. We're all very, very sad."
Bookey is currently held without bail in juvenile custody before a preliminary hearing slated for 8 August.