GREENSBORO, N.C. (AP) — Eight people stormed a high school classroom and attacked a 14-year-old girl in an incident thought to have stemmed from an earlier fight at a school bus stop, a North Carolina sheriff’s office said.

The Guilford County Sheriff’s Office said Thursday that a 16-year-old female student helped the group get inside Southern Guilford High School and led them to an upstairs classroom. The sheriff’s office described the group as six students and two adults and say they assaulted the 14-year-old student, who suffered facial injuries.

Faculty, administration and a school resource officer responded but by then the attack was over, the sheriff’s office said. The group ran away from the classroom and made it out to the parking lot, where they were stopped, according to authorities.

Capt. Brian Hall told WFMY that an adult who joined the group is a parent of a student at the high school.

“That was a deeply disturbing part for us,” Hall said. “You look at parents as the ones who are supposed to be giving the kid guidance as to how to handle these types of things, not encouraging it.”

Charges were still pending on Friday. Investigators are using surveillance video, cellphone video and witness testimony to determine exactly what happened.