Alyssa Bustamante had a troubled childhood (Image: Youtube/Kazzy4life)

In what stands as one of this century’s most disturbing murder cases, a teenager took the life of a nine-year-old girl simply to satisfy her morbid curiosity.

Alyssa Bustamante enticed her neighbour, Elizabeth Olten, into the woodland where the 15-year-old strangled her before slashing her throat and wrists. She subsequently interred the child in a makeshift grave.

On an October evening in 2009 in St Martins, Missouri, Elizabeth had been playing outdoors with her friend, Emma. When she failed to return home, authorities were alerted, sparking an extensive search involving hundreds of local residents scouring the forested terrain for any trace of the missing youngster.

Federal agents were brought in amid fears she might have fallen victim to a sexual predator. It emerged, however, that Emma’s half-sister, Alyssa, had appeared to join the girls during their play.

Before long, an unfilled shallow grave was discovered close to Alyssa’s residence, which she confessed to having excavated “for fun.”

FBI operatives, growing suspicious of the teenager’s conduct, proceeded to search her property, and their findings were deeply unsettling.

Her bedroom presented a horrifying scene: walls adorned with sinister scribblings and sketches, featuring images of a faceless figure and disturbing phrases such as ‘I cut to see blood because I like it’.

Alyssa was a deeply troubled adolescent with a documented history of depression, self-injury and suicidal behaviour. Investigators discovered that her father was imprisoned for violent offences, whilst her mother struggled with substance abuse and had endured repeated spells of incarceration.

The teenager and her siblings were brought up by their grandparents who did their utmost, yet she was already deeply troubled. Alyssa underwent a ten-day stint in a psychiatric facility in 2007 following a suicide attempt, which left lasting marks on her arms.

Alyssa Bustamante was found guilty of second-degree murder (Image: Youtube/Kazzy4life)

A disturbing YouTube clip subsequently surfaced depicting Alyssa urging her younger brothers to make contact with an electrified fence, whilst cheerfully commenting: “This is where it gets good… we get to see my brothers get hurt.”

Her personal diary unveiled an even more sinister aspect, including setting fire to her grandparents’ home. The final entry, penned on the day Elizabeth perished, had been obscured, but subsequent examination revealed it stated: “I just ******g killed someone. I strangled them and slit their throat and stabbed them now they’re dead. I don’t know how to feel atm [at the moment].”

She subsequently wrote: “It was amazing. As soon as you get over the ‘ohmygawd I can’t do this’ feeling, it’s pretty enjoyable. I’m kinda nervous and shaky though right now. Kay, I gotta go to church now… lol.”

Alyssa entered a guilty plea to second-degree murder at age 18. Her legal representatives highlighted her psychological difficulties, history of self-injury and potent antidepressant medication as mitigating circumstances.

The perpetrator herself showed contrition, stating, “If I could give my life to get her back I would. I’m sorry.”

However, the prosecution argued that she meticulously orchestrated the murder for her own amusement. In 2012, she was sentenced to life imprisonment with a minimum term of 35 years.

During her sentencing, Alyssa addressed the court, stating: “I know words can never be enough and they can never adequately describe how horribly I feel for all of this.”

Elizabeth’s mother, Patty Preiss, labelled Alyssa as “an evil monster” and expressed her deep hatred for her on the first day of the teenager’s sentencing hearing.