UNION TOWNSHIP (Union) — Union High School was placed on lockdown twice on Friday.

The first time was because of students who had brought a knife and a hammer to school. A later lockdown ensued because of panic fanned by social media, injuring at least one of the school's 2,200 students.

Police were first called in the morning when two students were spotted with the weapons, according to Union County Acting Prosecutor Lyndsay V. Ruotolo. The students were removed from the school. Officials did not say whether the students will face charges as juveniles.

Township police told RLS Metro Breaking News that a student brought a hammer to school because of an ongoing argument with another student.

Ruotolo said the second lockdown was put into place after school security heard a report that a student may have had a firearm.

As the story spread, a large group of students ran from the building before police arrived. One student suffered minor injuries during the escape, according to Ruotolo.

Police from several law enforcement agencies assisted township police with a building sweep, which did not find weapons. The circumstances that led to this lockdown remain under investigation.

Lockdowns and drills addressing school shootings have become a routine. In December 2016, the state enacted a law mandating monthly security drills in addition to fire drills. The security drills allow schools to practice procedures in the event of a bomb threat, evacuation, lockdown or a shooting.

During lockdowns, students and staff generally will lock themselves in classrooms and nobody except school authorities and law enforcement and emergency personnel are allowed to enter or leave the grounds.

In a letter to parents Friday night, Principal Mark Hoyt blamed social media for spreading a false report.

"It was disheartening that various social media platforms were used to spread a false narrative regarding today’s events. Misinformation only adds to the fear and anxiety already felt by parents, students, and staff," Hoyt's letter says.

Hoyt also said that he understood the frustration of parents when they could not get immediate answers about the lockdown.

"We strive to give as much information as possible as soon as we are able to; however, due to our responsibilities to the safety and security of the students and staff, we are not always able to disseminate this information during an active event," Hoyt writes.

Contact reporter Dan Alexander at Dan.Alexander@townsquaremedia.com or via Twitter @DanAlexanderNJ

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