A teenager was arrested Monday for recording two other teens having sex at a Bronx high school and then sending the footage, which he also posted on Facebook, to an underage girl, police said.

The 17-year-old filmed a 15-year-old girl and a 16-year-old boy having sex in a stairwell at William Taft High School on Jan. 19, a police source said. He then posted the footage online and allegedly sent it to a 14-year-old girl.

The school was alerted to the video and notified the NYPD.

Detectives determined that the alleged filmmaker was Isiah Pacheco and he was charged with disseminating indecent material to minors for sending the video to an underage girl, the NYPD confirmed.