At just 15 years old, she and her boyfriend massacred 5 members of her family.

A teenage girl has been accused of killing five members of her family and injuring two others with the help of her 16-year-old boyfriend.

The couple, aged 15 and 16 – whose identity has not been made public because they were arrested but not yet formally charged – allegedly carried out this massacre in several locations in East St. Louis, Illinois in the United States, on Sunday, July 12.

Authorities have identified the victims: the girl's cousin, Devin May, 24; her half-siblings, Quentin Thompson, 21, and Shania Thompson, 25; her 74-year-old grandmother, Patricia May; and her 49-year-old aunt, Cherie May.

The girl's father, Marcus May, said he was devastated by the tragedy when speaking about the mass shooting.

He claimed to have received a call from his child's mother five days before the shooting, warning him that their daughter had run away from home stealing his gun, the St. Louis Post-Dispatch reports.

Marcus May, who shares custody of his daughter, explained that she had been having problems at school in the months leading up to the shooting, which had prompted him and the mother to withdraw her from school and homeschool her.

According to him, this decision infuriated his daughter. The young girl, who lived with her mother, had already run away from home several times and stolen her mother's credit card.

Marcus May added that his ex-partner had warned him that their daughter was participating in a disturbing group chat with her boyfriend and other teenagers, where they were discussing killing her family members. However, he had not taken the threat seriously.

The father stated that his daughter's disturbing behavior had worsened until she stole her mother's gun a few days before the tragedy.

On the day of the bloodbath, he recounted that the grandmother of the young girl, Patricia, who was killed in the shooting, had called her granddaughter to beg her to come home, insisting that she could "manage" her behavior.

Meanwhile, Marcus May said he had contacted the boyfriend's parents to ask them to keep their son away from his daughter.

The girl's mother then reported her missing and notified the police about the theft of the weapon, but several days passed without any news of her.

On Sunday morning, Marcus May recounted waking up to numerous missed calls and messages, immediately realizing that something terrible had happened.

Police indicated that the victims were killed in several locations in East St. Louis. Shania Thompson was found in a car behind an abandoned property near Mr. May's home.

His brother, Quentin, was found nearby, on the other side of Interstate 64.

The other three victims were all discovered in the Samuel Gompers apartment complex.

Two other people, who have not been publicly identified, were also hit by gunfire during the shooting, but survived despite serious injuries.

Illinois State Police Commissioner Brendan Kelly described the events as a "targeted mass shooting" and confirmed that the teenagers had been arrested. However, they have not yet been formally charged.

See photos of the victims below…