(AP) — Just in time for Halloween, Jesuit scholars have joined a whole new generation of horror buffs in St. Louis to recount the supernatural incident that inspired one of the most terrifying films in movie history.

The monthlong demon-purging ritual in 1949 at Saint Louis University’s former Alexian Brothers Hospital involved an unidentified suburban Washington, D.C., boy and formed the basis for William Peter Blatty’s 1971 novel, “The Exorcist.” The film of the same name was released two years later.

On Tuesday, the university hosted a panel about the ritual and treatment of the 13-year-old boy.

The Rev. Walter Halloran was the last surviving Jesuit to participate in the exorcism before his death a decade ago.