Four people have been charged with plotting to attack a rural American Muslim community named Islamberg
The three men and one teenager had access to 23 rifles and shotguns and three homemade bombs when they were arrested this weekend, police said.
"They had a plan in place," Greece police chief Patrick Phelan said.
"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."
The men charged were 20-year-old Brian Colaneri, 18-year-old Andrew Crysel and 19-year-old Vincent Vetromile, along with a 16-year-old student who cannot be named.
He said homemade bombs packed with black powder, ball bearings and nails were found wrapped in duct tape in the 16-year-old's home, along with guns legally owned by the group's family members.
The alleged plot targeted a small enclave in upstate New York, where families of mostly-African American Muslims relocated in the 1980s to set up an religiously-oriented community to escape urban crime and overcrowding.
Operated along with 21 similar communities by the Muslims of America, it is inspired by the teaching of Sheikh Mubarik Gilani, a Pakistani cleric.
The 200-or-so residents of the hamlet tend to commute to jobs in other towns and keep a fairly low profile, according to reports.
But the settlement has been targeted by far-right organisations, who have made films claiming it is a "compound" where militant training is organised. The rumours have been dismissed by authorities.
Robert Doggart was in 2017 sentenced over a plot to burn down a mosque, school and community centre in the town, and of recruiting people to join him in the attack.
After the weekend's charges, Mr Phelan did not rule out the possibility that further arrests could take place during the investigation.
Three of the suspects were boy scouts, and the teenager was a pupil at Odyssey Academy in Greece.
The alarm was raised at the school, after another student overheard the boy saying "he looks like the next school shooter, doesn't he" as he showed students a picture of another boy on his phone.
The students were interviewed and a "plot to attack an Islamic community in Delaware county" uncovered, Mr Phelan said.
The schools district superintendent said the students who reported the suspect "changed the narrative" by reporting their concerns.
"They trusted their instincts and used what they learned in school," Kathleen Graupman said.Responding to the incident, the Council of American-Islamic relations called for federal charges.
"Anyone accused of plotting an act of violence targeting a religious minority should face state and federal hate crime and civil rights charges commensurate with the seriousness of their alleged actions," executive director Afaf Nasher said.