The 1973 classic "The Exorcist," an Oscar-winning horror film that is still considered to be one of the scariest ever made, and the book of the same name, were not simply imagined, but inspired by demon-purging rituals that took place for a month at St. Louis University in 1949.

According to IndieWire, William Peter Blatty's terrifying book and William Friedkin's film adaptation helped usher horror out of the B-movie ghetto and into mainstream success. The story centers around troubled young girl Regan (Linda Blair) who has been posessed by a sadistic demon, and her neurotic, single mother Chris (Ellen Burstyn), and the film, which precedes the rise of the slasher genre in the late '70s, speaks on many cultural and social anxieties surrounding young girls and women and the changing female body, as IndieWire's Katie Walsh writes.

"It's shocking to see such a young and innocent body so abused and destroyed. It's even more shocking that the nature of possession means that we see her do these things to herself. This is horrific because of her body's youth and purity, but also because we have stricter social expectations about the behavior of little girls," she writes, referencing the horrors that Regan endures - and inflicts on herself - while possessed. 

The "real" exorcist on which the book and film are based, however, involved the treatment of a young boy from Washington D.C. The events were discussed by a panel in St. Louis on Tuesday, Oct. 29, according to the Associated Press, attended by around 500 people.

"I'd like to believe it's the real thing," Grummer-Strawn, a theology and sociology student from Atlanta told the AP. "But you just can't know. That's part of why we're here. It's the pursuit of truth. And it's such a great story." 

Speakers and guests at the panel included Thomas Allen, author of the 1993 account of events that took place at the school's former Alexian Brothers Hospital, in which a boy named "Robbie" reportedly suffered from demonic spirits, though it was possible he was mentally ill or had been sexually abused. The 13-year-old boy arrived to the hospital in the winter of 1949, where a distant cousin, Father William Bowdern, led the month-long exorcism after consulting with the archbishop of St. Louis.

"He talked more about the boy, and how much he suffered, and less about the rite," Allen said of Bowerden's assistant at the time, Rev. Walter Halloran. "Here was a scared, confused boy caught up in something he didn't understand. He told me, 'I simply don't know,' and that is where I leave it. I just don't know." Bowdern passed away in 1983.

Many non-students in the audience at the panel discussion spoke of their own experiences in relation to the young boy's infamous exorcism, and recalled how much the film had frightened them.

"I saw the movie when I was 19 years old and it scared me to death," Gary Mackey, a 59-year-old accountant who left campus early in 1973 to see the film. "I think it's the scariest movie ever made."