Threats and rumors of threats made against New Jersey public school districts led one of them to cancel classes on Friday.

School districts are on edge all around the state following the shooting at Stoneman Douglas High School in Parkland, Florida, that left 17 students and teachers dead.

A threat on Instagram kept Nutley public schools closed, according to Nutley Police. The content of the video posted was not disclosed, but police said they are speaking to the individuals in it.

"Preliminarily, there doesn’t appear to be an active threat to any of the schools but we must finish this process," police wrote in their Facebook post.

Police asked parents to remain calm as the investigation continued.

According to TAP into Nutley, the video showed a Nutley High School senior at a firing range with some friends, accompanied by the song "Pumped Up Kicks." The 2011 song by the group Foster the People includes lyrics about outrunning bullets from a gun.

"All the other kids with the pumped up kicks, you'd better run, better run, faster than my bullet," read the lyrics.

Superintendent Dr. Julie Glazer said in a statement on the district website that she made the decision to "err on the side of safety" and close all schools on Friday.

Jackson Police Captain Steve Laskiewicz, in a post on the department's Facebook page, said his department investigated a rumor on social media that a student posted a list of students he may wish to harm.

"There is no known credible threat regarding any of the township schools at this time and contrary to any rumors being circulated, the department does not have any information that would support students staying home tomorrow," Laskiewicz wrote.

Jackson Public School spokeswoman Allison Erwin defended the decision to hold class on Friday. "Please know that if there was a cause for concern, we would not hesitate to take action to protect our schools. The safety of our students and staff is our most important priority," Erwin wrote in an email.

Police already increased their presence at all district schools following the Florida shooting.

Monroe School (Middlesex County) Superintendent Dr. Michael Kozak sent an email to parents discussing threats made against district schools that are being investigated.

"No credible evidence has been substantiated regarding any type of school shooting to occur in the Monroe Township Schools," he wrote.

He said one threat on social media originated in South Carolina and has been removed.

Kozak also contacted parents via phone to assure them district schools would have an increased police presence on Friday.

In an email, Kozak told New Jersey 101.5 he appreciated the work of police to investigate tips and rumors.

"I appreciate their hard work and support and understanding of our parents who reached out to us to ask for information, and thank us for being thorough and keeping them informed of our investigative results," Kozak said.

A district parent who did not wish to be identified said in one chat group, a sophomore claimed Friday would be "death day," and threatened to shoot up the high school. The parent reported the threat to police, who said they had already spoken to the student and his parents.

Many Monroe students expressed concern in social media conversations about the threats, and were considering staying home on Friday.

Police in Gloucester County's Monroe had to clarify that their schools were not threatened. "There is NO credible threat to Williamstown Middle School or the Monroe Township School District in Gloucester County," police wrote on their Facebook page.

Freehold Township superintendent Dr. Rose Kasun sent a letter to parents that security has been increased at district schools and they have an emergency plan in place.

Monmouth County Prosecutor Christopher J. Gramiccioni said his office works with local police and school safety officers to investigate all threats.

“Whenever information regarding a threat involving a student is communicated to our office - by either the police, the school or a member of the public – a detective from our office is immediately assigned to do an appropriate investigation. That investigation includes speaking with witnesses, including often the student himself, and reviewing available electronic forensic evidence, if applicable to the situation, to determine the credibility of the threat," the prosecutor said.

Contact reporter Dan Alexander at Dan.Alexander@townsquaremedia.com or on Twitter @DanalexanderNJ.

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