14-year-old 'psychopath' tortured brother's girlfriend hoping to make her 'first kill', police say.

Kali J. Bookey, a 14-year-old teenager living in New Richmond, Wisconsin, has been charged as an adult with attempted first-degree intentional homicide.

She is being held in a juvenile detention center for allegedly breaking into her brother’s girlfriends home and spending hours beating her, suffocating her, cutting her and slitting her throat with shards of glass from a broken bowl, the Daily Mail reports.

The 15-year-old victim is still in hospital suffering from very serious injuries.

Kali Bookey allegedly reiterated her plan to the victim, saying that she had carefully thought out this attack for over a week and a half, riding past the house regularly on her bike to take notes on when people came and left.

Kali J. Bookey. Image: Facebook.

She allegedly described her victim as the 'first kill' but hinted that she was a 'psychopath and would probably kill again.' It is claimed she then asked the 15-year-old girl whether she would like to 'die right now' or 'bleed out'. Her victim reportedly chose to bleed out.

When Bookey allegedly confessed to police what had happened, after first saying it was the work of two men in ski masks, police claim she admitted that she had grown immense hate for the victim because of how content she made Bookey's 16-year-old brother.

While she allegedly told the victim she hoped this was her 'first kill', Bookey reportedly later told police that she had only meant to scare the girl long enough for her to leave town so that her brother would be closer to the family again.

Police say Bookey spoke about the attack in a very 'calm and unemotional way' as she went into great detail about the near-fatal blows she inflicted on the victim. Her brother has spoken out since the attack, saying that the victim is 'doing well'.

Kali is in a juvenile detention center. Image: Facebook.

"She is very calm, and she is not at all shaken by it, just shocked my sister would do it. She says she loves her scars because they look cool, and she's only upset that her favourite dress got ruined. As she was bleeding to death on her floor, she sent me a message asking to have Bookey on her tombstone instead of her last name," he finished.

The victim and Bookey's brother are planning to marry next June.

Normally the press wouldn't reveal the name of a minor in a criminal case, but in Wisconsin, juveniles accused of first-degree homicide or attempted first-degree homicide, who are over the age of 10, can be tried as adults. This was the case for Kali Bookey, and thus her name can be mentioned here.

She will be due in court again on August 8, but will not return to her family home in between time.