BAYONNE — A 13-year-old was arrested for sending a threat late Monday night via Twitter.

Bayonne Mayor Jimmy Davis said in a Facebook post the city resident was charged with false public alarm and terroristic threats for a tweet being considered a copycat of the initial threats that closed the district's 12 schools on Monday. Bayonne Police worked with the Hudson County Prosecutor's Office and State Police to find the sender.

Davis had said the threat now attributed to the 13-year-old read "nice, you evacuated. I got 4 more days to shoot up the school..."

A threat was sent on Friday via Twitter to "shoot up" several schools mentioned by name, but the message was brought to the attention of police until Sunday, authorities have said. The account used was deleted immediately after the message was sent.

While that message was being investigated, a second message was sent via Snapchat on Monday morning with a similar threat, authorities said. Because police could not determine if the message was credible or not classes were cancelled.

Davis said the investigation continues into the initial threats.

Franklin Middle School in Somerset County was put on lockdown searched after a student found a bullet on the ground on Tuesday afternoon, according to Franklin Township Police. No other bullets or ammunition were found.

A 17-year-old male student at Franklin High School in the same district was arrested at the end of February for having a 9 mm semi automatic handgun in his backpack. He was charged with possession of a firearm and second-degree possession of a weapon for an unlawful purpose.

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