Police Chief Patrick Phelan says the investigation began last week when a 16-year-old student showed a photo of another person to his friends and made a comment, claiming that the person looks like he could be a school shooter.
Others in the cafeteria alarmed by the comment told school officials. Through a series of interviews, Phelan says authorities uncovered a plot to attack the community of Islamburg in the Catskills.
He says during the probe, police recovered 23 guns and 3 homemade bombs.
“If they had carried out this plot, which every indication is that they were going to, people would have died. I don’t know how many and who, but people would have died," Phelan said.
Those arrested include 20-year-old Brian Colaneri of Gates, 19-year-old Vincent Vetromile of Greece and 18-year-old Andrew Crysel of East Rochester.
A fourth person, the 16-year-old who originally made the comment that led to the police investigation, was also charged. All of those arrested face charges of criminal weapons possession and conspiracy and it's possible there could be federal charges later on.
Greece School Superintendent Kathleen Graupman is glad that students and adults followed up on remarks that worried them.
“We are also incredibly grateful about the young people who refused to stand idly by, students trusted their instincts, and what they’ve learned from us at school. These students came forward with information supporting the idea that if you see something, you say something,” Graupman.
The Associated Press reports that followers of a Pakistani cleric settled Islamberg in the 1980s to flee crime in New York City. NPR says about about 200 people live there.
In recent years Islamberg has become the target of suspicion and conspiracy theories among right-wing groups and conservative media, including the Alex Jones program Infowars. One broadcast on Fox News suggested that people in the Islamic "compound" were "stockpiling guns" in response to the election of President Trump.
In 2017 a Tennessee man was sent to federal prison for nearly 20 years after plotting to burn down Islamberg's mosque and school. At the time, then-Attorney General Jeff Sessions described the plot as an attack on religious freedom. "People of all faiths have the fundamental right to worship freely, and this administration will not tolerate attempts to violate that right," Sessions said.
State police and the FBI have regularly debunked claims that Islamberg poses a danger to the wider community. Still, anti-Muslim activists regularly hold protests nearby. Lisa Joseph, a conservative activist from Syracuse, joined a rally in 2017 and told NPR that she would "not tolerate ISIS training camps, militant-style training camps, radicalized training camps" in upstate New York.
A spokesman for the Islamberg community says it will hold a news conference on Wednesday.
NPR contributed to this story.