Colchester High School was one of the more than 20 K-12 schools in Vermont that received what turned out to be phony threats of violence Wednesday.

Colchester Police Chief Douglas Allen says the department’s emergency communications center received a phone call around 9:45 a.m. In an accented voice, the caller said that an attack had occurred and “that some students and a teacher had been injured.”

As officers responded, the school was locked down, said Superintendent Amy Minor.

Meanwhile, In an automated phone call, parents were told other high schools had received similar threats and officials believed they were a hoax.

Allen says students were in lockdown for about 30 minutes before the threat was determined to be a hoax. The school released a statement saying, “at no time were our students or staff in danger; however, the situation was frightening for everyone.”

Jay Nichols, executive director of the Vermont Principals’ Association, said the fake threats were “an incredible act of selfishness.”

“It causes unnecessary fear and trauma in schools for families, students and school employees,” he said. “School shootings are a real thing, and sending a hoax of this type plays into the narrative that schools are unsafe, when we know for the vast majority of students, schools are the safest.”

Minor said the incident, while posing no actual threat, underscored the importance of preparation including regular lockdown drills.

“Of course, we take the safety of our students very seriously,” she says. “We were very pleased with the response, and it really shows that practicing lockdown drills does create muscle memory for students and staff, so they know what to do if we’re ever in a situation that we need to be in a lockdown.”