Jason Graham, 24, of Holland, Michigan, pleaded guilty Friday, according to the U.S. attorney’s office in Vermont.
Prosecutors said Graham was involved in an online dispute with a group of students from Green Mountain Union High School in February 2019 when he made threats on Facebook to "shoot up" the school in Chester.
Three days later, he had someone else call the school to say that he had placed a bomb in the school and had sharpshooters outside, prosecutors said.
More than half of the school’s student body skipped school in response to the first threat, and the bomb threat drew a massive law enforcement response, according to the U.S. attorney’s office.
Graham later was convicted in Michigan of illegally possessing a firearm.
He faces up to one year plus one day in prison for the Vermont conviction.
His attorney could not be reached for comment Sunday.