NEW LENOX, Ill. (AP) — A former student at a suburban Chicago Catholic high school has filed a lawsuit claiming he was sexually abused more than 20 years ago by the school's former principal.

Bob Krankvich says he was repeatedly abused during his freshman and sophomore years at Providence Catholic High School in New Lenox by Father Richard McGrath, a member of the Augustinian Order, which is also named in the lawsuit.

The now 36-year-old Krankvich alleged Thursday that McGrath threatened him and his family with arrest if he revealed the abuse.

New Lenox Police Chief Bob Sterba says Krankvich came forward after a Providence Catholic student reported she saw a picture of a naked adolescent boy on McGrath's cellphone.

Sterba says the 71-year-old McGrath, who retired in December, refused to be interviewed by police or hand over his cellphone. McGrath's attorney Patrick Reardon declined comment.

The Diocese of Joliet says it, the school and the Augustinian Order will fully cooperate as the case proceeds.