Three middle school students in western New York plotted a lethal attack on their school that was thwarted after an online threat by one student led law enforcement authorities to open an investigation, officials said on Friday.
The students, whose names were not released because of their ages, were charged on Thursday with second-degree conspiracy and accused of planning an armed assault on the Carl I. Bergerson Middle School in Albion, N.Y., said Joseph V. Cardone, the Orleans County district attorney. The students were released to their families under the supervision of the county’s Department of Probation, Mr. Cardone said.
The plot emerged after one student threatened another online on Nov. 1, and then suggested that other children were also at risk, Mr. Cardone said. That prompted law enforcement authorities to open an investigation that led them to two other students who were conspiring with the first student, he said.
The inquiry turned up evidence of what Mr. Cardone called a “credible threat.” The evidence included an unspecified number of guns in the students’ homes, all of which, Mr. Cardone said, were legally owned by adult family members.
“This was concerning to us obviously because of the extent to which there was planning involved,” he said. The planning, he added, included a specific date for the attack.
Roland Nenni, the Albion police chief, said at a news conference that while there was a set date for the attack, “We did not feel the attack on the school was imminent,” according to The Daily News of Batavia.
The students’ plan, Chief Nenni said, was “to enter the school with explosive and incendiary devices and firearms to kill and injure students and staff.”
Michael S. Bonnewell, the Albion Central School District superintendent, did not return a call seeking comment on Friday.
In a letter to parents and staff members the day before the students were charged, Mr. Bonnewell said that the authorities were investigating reports of “threatening messages and images” on Discord, a voice and messaging app that is popular with players of online games.
Mr. Cardone declined to comment on whether any of the students who were charged had communicated via Discord. He said that the investigation was continuing and that computers, cellphones and laptops had been seized and were being examined as part of the inquiry.
Sean Li, the director of trust and safety at Discord, said that the company had “a zero-tolerance approach to harassment and illegal activity on our platform.”
Mr. Bonnewell said in the letter that the students involved in the original messages had been “removed from school pending the completion of the investigation.” Mr. Cardone said on Friday that the students had been expelled.
Albion, which has a population of around 6,000, is about 30 miles west of Rochester, a short drive from Lake Ontario and on the Erie Canal.
That three students rather than a single person are accused of plotting to attack the school makes the Albion case “very unusual and uncommon” in New York State, said William Duffy, a spokesman for the New York State Police.
In September, three students in California were arrested on charges of making terroristic threats. The authorities there said the students had plotted a shooting attack on a high school in Desert Hot Springs. The police seized a Glock semiautomatic handgun and a .357 magnum revolver.
The California arrests came after a staff member of the local school district noticed a social media post threatening violence, prompting school officials to alert the police, officials said.
An adult convicted of second-degree conspiracy in New York would face up to 25 years in prison, Mr. Cardone said. Because their cases will be handled in family court, he said, the Albion students face punishments ranging from being placed under the supervision of the county’s parole department to serving time in a juvenile detention center.