Two teenage girls were detained in Riverside County on suspicion of planning a mass shooting at Corona High School, authorities said. The 15-year-old suspects, one from Corona High and the other from nearby Norco High School, allegedly targeted a list of students and teachers in a planned attack motivated by revenge.

The investigation began on Oct. 6 when the FBI alerted the Corona Police Department to social media activity suggesting a threat against Corona High School. Following this lead, police arrested the first girl and subsequently identified the second suspect. Due to their age, the names of the teens have not been disclosed.

According to Corona Police Lt. Robert Montanez, the girls had compiled a list of potential victims but also appeared to intend a broader assault on the school itself. The exact number of names or their identities were not provided. Law enforcement officials said the teens had spent several months researching previous school shootings and methods for acquiring firearms, although no weapons were obtained.

Montanez characterized the motive as revenge, though further details were not available. He also stated that the relationship between the two suspects and the duration of their acquaintance remain unclear. Both girls are now in custody, facing charges of conspiracy to commit murder, and the Riverside County district attorney’s office is reviewing the case.

The police official noted that the case is uncommon given that mass shooting plots typically involve male perpetrators acting alone. “Historically speaking, the vast majority of people who commit these kinds of offenses and who follow through on mass shooting incidents are generally male,” Montanez said. He also highlighted the effectiveness of receiving information from social media platforms, which officials credited with helping to prevent the planned attack.

Authorities continue their investigation into the matter, emphasizing the importance of early detection and response in averting school-related violence.