DOWNINGTON, Pa. (CBS) - Another case of teenage bullying caught-on-videotape has surfaced, this time in Downingtown.

Pennsylvania State Police say they filed charges against three 13-year-olds from West Chester, Pa. and Downingtown, for assaulting a 13-year-old boy on a Downingtown School District bus.

Police say the attack took place January 20th, but they only became aware of it when they were provided with a videotape of the incident made by one of the accused students.

Police say the video shows the victim being hit and shoved by the others — two girls and a boy — aboard the moving bus. All four teenagers are students at Downingtown Middle School.

Police say school officials assisted in the investigation.

Reported by Pat Loeb, KYW Newsradio