A person claiming to be a student threatened on social media to “shoot up” an elite high school in Brooklyn — and police are now investigating the sick posts, cops said Sunday.

“I’m going to shoot up my school Millennium Brooklyn High School New York with a MP15 assault rifle and a Glock 17 pistol with hundreds of rounds of ammunition in a few weeks and Livestream it on my Instagram,” the person wrote on the site Omegle on Thursday.

An employee at the Park Slope school reported the disturbing threat to police at 9 a.m. Friday, an NYPD spokeswoman said.

“We’re investigating it,” Detective Denise Maroni said.

The post also said the shooter would blast “dancin military style and abba gimme gimme eurobeat” music during the shooting.

“I hope to take at least 15-30 people with me mostly in the classrooms or hallways, plus some people fleeing the building,” the post said.

The alleged wannabe shooter vowed to not surrender to police and would “shoot through the windows to get them and before I do it I’ll send a link to my stream to everyone.”

The person then lists the names of more than a dozen students to be killed.

The building where the school is located contains several different schools. 

An employee from Park Slope Collegiate, which is also in the building, sent parents an e-mail informing them about the threat.

“Last night, an unknown person posted a threat to one of the schools on our campus, Millennium Brooklyn High School, on a site called Omegle,” the message reads.

“The post appears copy and pasted from social media threats that have been made in previous months to schools throughout our area, but it does include the school name and the names of some students. We are taking the threat seriously…”

There have been a series of mass shooting threats at New York City and Long Island schools over the past week in wake of the slaughter at Robb Elementary School in Uvalde, Texas.