CAMBRIDGE, Neb. (AP) — Authorities say four teenagers are facing charges that they planned to attack a high school in south-central Nebraska.

The Furnas County attorney charged two 18-year-olds and two 17-year-olds with felony terroristic threats related to a plan to attack Cambridge High School on Nov. 30.

Court records allege the students had been discussing an attack for months. When one student transferred to a different school, they tried to recruit another student.

One student told police he thought the plan was a joke but wasn’t sure if the others felt that way.

Cambridge Public Schools Superintendent Greg Shepard told NTV the school received a call from a parent about a potential threat, prompting it to contact the sheriff’s office and state patrol.