School officials in several districts across New Jersey are investigating threats following the tragedy out in Parkland, Florida.

Lockdowns, early dismissals and police officers in hallways were used as safety precautions in four New Jersey school districts in the 48 hours following the massacre of 17 students and faculty at the Marjory Stoneman Douglas High School in Florida on Wednesday.

Officials say a bullet found in a school hallway by a student prompted a lockdown and search of a middle school in Parsippany Friday.

Authorities say they don't know who brought the bullet into Brooklawn Middle School and why, but in the wake of the massacre in Florida, they’re not taking any chances.

Also on Friday morning, a male high school student in East Brunswick was arrested and charged with terroristic threats for an online comment. According to the superintendent, a parent and teacher notified district staff of the posting. A security officer escorted the student to the office, where he was questioned by East Brunswick police before being taken into custody.

The superintendent thanked the police for their "swift action" and said the community needs to remain vigilant.

Police in Nutley say they are still investigating a suspicious Instagram post. Schools were closed there Friday as police checked all the grammar schools and sent K-9 units through the middle and high school.

On Thursday evening, police were called about a 14-year-old male Franklin High School student who made a threat on social media. Though the threat was not determined to be credible, the 14-year-old was arrested and charged with third-degree terroristic threats.

In response to both the Parkland shooting and the arrest of one of their own, East Brunswick police are sending more officers into the schools, augmenting an already 71-member security force of retired officers.

The district saying those officers will remain throughout the school year.