Threats made against two Suffolk County high schools -- one in Mount Sinai, the other in West Islip -- resulted in the arrest of a 15-year-old student in one case, while police are continuing to investigate the other on Tuesday, police said.
Suffolk police said the student, a ninth-grader, was arrested Monday in connection with postings on the social-media app Yik Yak threatening a shooting at Mount Sinai followed by a bombing.
The boy has been charged as a juvenile and is due in Family Court on Tuesday.
Police said the second incident involved threats of a shooting and bombing at West Islip and said those threats are being investigated. Police were at the school Tuesday with additional security procedures in place. Police did not detail how the West Islip threats were uncovered and declined to say whether there is a suspect in the case.
A message on the West Islip website reads: "On Monday evening the police were called to the high school to investigate a bomb threat that was reported to the Suffolk County Police Department by a caller who became aware of the alleged threat. After a thorough search of the building, it was determined that the threat was not credible and the campus is safe.
"Local law enforcement agencies are taking this incident very seriously and are conducting a thorough investigation. Classes are proceeding today [Tuesday] as regularly scheduled. Increased security and SCPD are in place. There is no further information to share at this time as this is an active police investigation."
In the case of the Mount Sinai threat, police said, the student posted using the anonymous Yik Yak app that "there would be a shooting at the school and then he was going to blow it up on Tuesday, 9/16."
The school notified police of the postings after being alerted to them by students and parents, police said. Sixth Squad detectives investigated the call -- and arrested the student.
He was charged with making a terroristic threat.
In a statement released Tuesday afternoon, Mount Sinai School District Superintendent Gordon Brosdal said: "Late Monday afternoon the Mount Sinai School District became aware of threats made toward the high school via social media. District administration immediately notified police who worked to identify the alleged culprit, a ninth-grade student at the high school, and subsequently made an arrest. The district has stayed in constant contact with law enforcement officials throughout the investigation and, as a precaution, police will continue to have a presence at all three schools [in the district] today. The safety and security of our students and staff is of the utmost importance."
The statement followed a letter from Brosdal to district parents and guardians Monday in which the superintendent warned of "misuse and abuse" of new technologies and social media apps like Yik Yak -- and stressed the need for continuing efforts to teach students "appropriate behavior."
Brosdal suggested parents monitor against the potential misuse of other social media apps such as Snapchat, Kik, Whisper and Tinder, as well as review the age-appropriateness of cellphone settings -- to the extent they consider blocking inappropriate apps or settings.
He also urged parents and guardians to "have a discussion with your child about how to treat others with respect and stress the importance of having relationships only with those who are respectful in return."
Brosdal said the "anonymity" of potential posts using some of these apps "allows individuals who may have malicious intent to write comments about others that may be hurtful, harassing and sometimes quite disturbing."
Police school resource officers will have a presence at the school Tuesday, police said.