A violent incident at a Pennsylvania high school on Wednesday morning has left multiple victims as authorities try to break down what happened.

Franklin Regional High School was put on lockdown early this morning after a security officer called police to report a stabbing and requested medical assistance. According to the Pittsburgh Post-Gazette, 20 people were injured in the incident, 4 of them seriously. Seven of the victims were between the ages of 15 and 17; as many as eight people were flown to a nearby hospital by helicopter.

A male suspect–a student at the school–is in custody, although police have not released his identity or a motive for the stabbings. Authorities released students from the elementary and middle schools nearby, and non-injured high school students were taken to Heritage Elementary where they were picked up by parents.

The school district released a statement on its website to the families of the students, saying, “A critical incident has occurred at the high school. All elementary schools are canceled, the middle school and high school students are secure. Additional information will be released as soon as possible. Please keep our campus clear of traffic.”

District Attorney John Peck has detectives monitoring the situation, but the FBI was also on the scene early this morning.

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