Updated

A developing plot to stage a "military-style assault" at a high school near the end of the school year has been foiled, authorities said.

One person has been charged in the ongoing investigation, which began this week after officials at Belvidere High School heard allegations that a 17-year-old senior male student was developing a hit list of students and teachers, State Police spokesman Capt. Al Della Fave said Wednesday night.

School officials notified Belvidere police, who soon got state police, the FBI and the region's Joint Terrorism Task Force involved.

State police detectives Michael Lamonaco and Kenneth Koenig, working with officials from the other agencies, then began a more extensive investigation and spoke with nine of the student's acquaintances, described by Della Fave as five juveniles and four adult males, all of whom live in or nearby White Township. Della Fave would not say whether any of them were also students.

"Investigators learned that the military-style plot was being developed, and that (those involved) had begun doing surveillance work at the school and were working to identify possible escape routes," Della Fave said.

Authorities notified the 17-year-old student's father, who voluntarily surrendered some guns in his house to authorities. Della Fave said that all the weapons were legally registered and that the father has been assisting investigators.

The student, whose name was not disclosed, has been hospitalized for a mental health evaluation, Della Fave said. He has not yet been charged.

James M. Shipps, 22, of , was charged with creating a false public alarm, making terroristic threats and hindering apprehension, Della Fave said. He was being held in the county jail on $50,000 bail. It was not immediately clear whether he had a lawyer.

Della Fave credited teamwork of local, state and federal officials with foiling what he said could have been "a truly horrible" incident.

"This is an example of the partnerships we need to have, and why it's important for people to report suspicious activity," he said.