The two girls, ages 15 and 16, planned on placing pipe bombs around the school and using guns to then pick off panicking students and teachers, the Montgomery County Sheriff’s Office alleged.

One of the girls accused of plotting a pipe bomb attack and shooting at Memorial High School was ordered to be held at a Harris County facility for juvenile defendants after the 16-year-old girl's mother testified Friday about her daughter's struggles with mental health.

The FBI says the plot involved pipe bombs and guns. The case spans two counties, with the girls attending two different Houston-area school districts.