A lector was punched by someone in the congregation as she left the altar during Mass Sunday at Cathedral Basilica of SS. Peter and Paul in Philadelphia.

The sudden attack was captured on the Facebook livestream of Archbishop Nelson Pérez, who called it a “senseless act of aggression.”

“Such behavior is unacceptable at all times, especially within the confines of a church building and during the celebration of the Holy Mass,” the archbishop posted on Facebook. “I was saddened to learn of this incident and regret that it took place. The lector who was assaulted received immediate attention and assistance from Cathedral staff members off camera. She did not require medical attention and is doing well based on the reports I have received.”

The Archdiocese of Philadelphia is working with police, who are investigating the incident during the 11 a.m. Mass, he said.

“Please be assured that there are safety and security plans in place for the Cathedral Basilica of Saints Peter and Paul,” Pérez continued “We welcome all visitors and work to provide for their safety. Violence has no place in our world and every life is a precious gift from God. Please join me in praying for everyone involved in today’s incident and for respect for our fellow brothers and sisters.”

The attack can be seen just after the 32-minute mark of the church’s Vimeo stream: