Millville police said the teen created an Instagram account where she posted two pictures of the high school and captioned the post “I’m coming” with a coffin emoji.
A concerned parent contacted police on Monday after seeing the post.
The teen was identified and charged with false public alarm and terroristic threats.
School officials said police will be present on campus for the next couple of days as a precaution.
“The police are involved and will continue to be an active presence in the next few days. It has been concluded by the police that there are no known threats to our school safety,” the school said on Facebook.