The 16-year-old was arrested after the school principal saw a threatening post on Instagram and contacted police. Newsday TV's Steve Langford reports.  Credit: Newsday/Alejandra Villa Loarca

A Bellport High School student made an online threat of a "mass shooting" at his school Thursday, Suffolk prosecutors said — just two days after 19 students and two teachers were killed, allegedly by an 18-year-old gunman, at an elementary school in Uvalde, Texas.

The 16-year-old student, who was not identified because he is a minor, created a post on his “Bellport Scholars” Instagram page Wednesday night that stated "bellport mass shooting tmr? shhh," according to Suffolk County District Attorney Ray Tierney.

“Thankfully this incident appears to be a terrible prank gone wrong and the accused had no capacity or intention to act on the threat,” Tierney said at a news conference Friday in Hauppauge. " … The youth had no access to guns nor did he have any intention to actually follow through on his threat."

Multiple people, including the high school principal, called 911, and detectives arrested the teen at his home in Bellport at 7:45 p.m. Thursday. The FBI also was involved in the investigation.

Suffolk police did not find weapons in the home, Tierney said.

The teen was charged with making a terroristic threat and aggravated harassment and spent the night in jail.

He was arraigned in the youth part of First District Court in Central Islip Friday and released on supervised release probation with GPS monitoring with a 9 p.m. curfew. 

Judge Karen Kerr said the teen is only allowed home and office visits, is prohibited from using social media, and must submit to alcohol and drug testing.

The teen, who is being represented by Suffolk County Legal Aid, which does not comment on pending cases, is due back in court Tuesday.

Tierney said the teen likely "did not understand the ramifications of his behavior" before making the post.

"This should be a cautionary tale for anyone thinking they can issue threats of this type online," Tierney said. " … This is not a joke. It will be taken serious."

Suffolk acting Chief of Detectives John Rowan said the teen had not previously made online threats. 

"I hope it's a one-time thing that we don't see again in Suffolk County," Rowan said.

Since the May 14 shooting in Buffalo when a gunman, allegedly targeting Black shoppers, killed 10 people at a supermarket, Rowan said police have tracked eight questionable or inappropriate online postings but determined they were all noncriminal in nature.

The high school student will receive "appropriate disciplinary consequence" as part of the district's Code of Conduct, Bellport Schools Superintendent Joseph Giani wrote in a letter to parents Friday.

On Thursday, there was a heightened police presence at the high school and middle school, with officials checking the backpacks of students as they came in and out of the building. The school was closed Friday in advance of Memorial Day.

When schools reopen Tuesday, Giani wrote, they will operate on a modified lockout schedule and classroom doors will remain closed at all times. 

"The safety of our students, faculty and staff are our highest priority, and steps are taken every day to ensure that everyone in our schools are safe," he wrote.

Since the Texas shooting, officers have been moved off patrol and to schools "to make sure everyone is comfortable," said Suffolk Police Commissioner Rodney Harrison. 

Tierney plans to convene a “School Safety Summit” in the next month with parents, teachers, school officials and law enforcement.

With Ted Phillips

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