#Rev. Bowdern was not to disclose his position and the location of the ritual, the fifth floor of Alexian Brothers Hospital.<ref name="Terry D. Cooper, Cindy K. Epperson - Stipulations">{{cite book|url =https://books.google.com/books?id=DXHqjYs3l5kC&pg=PA25&dq=Robbie++exorcism&lr=&cd=1#v=onepage&q=Robbie%20%20exorcism&f=false|title= Evil: Satan, Sin, and Psychology |quote= First, Bowdern himself would conduct the exorcism (a decision Bowdern had not anticipated and didn't really want). Second, a tedious diary would be kept concerning all the activities that would accompany the exorcism. And third, Bowdern was to tell no one what he was doing.|publisher = [[Paulist Press]]|accessdate = 2010-04-02}}</ref>
Before the exorcism ritual began, [[Walter Halloran|Rev. Walter Halloran]] was called to the psychiatric wing of the hospital, where he was asked to assist Rev. Bowdern in the deliverance.<ref name="Washington Post">{{cite web|url = https://www.washingtonpost.com/wp-dyn/articles/A18767-2005Mar8.html|title =Jesuit Priest Walter Halloran|quote= Father Halloran was the last living Jesuit who assisted in the exorcism in 1949 at a psychiatric unit in St. Louis. Father Halloran was a 27-year-old Jesuit scholastic at St. Louis University when a priest called him to the psychiatric wing at Alexian Brothers hospital. The Rev. William S. Bowdern was trying to help a 14-year-old boy from Mount Rainier who he believed was possessed by a demon, and he needed a strong man to help control the boy. A third Jesuit, the Rev. William Van Roo, also was there. "The little boy would go into a seizure and get quite violent," Father Halloran told the St. Louis Post-Dispatch in 1988. "So Father Bowdern asked me to hold him. Yes, he did break my nose." Father Halloran said he saw streaks and arrows and such words as "hell" on the boy's skin. Father Halloran told a reporter that the boy went on to lead "a rather ordinary life." A news account of the incident inspired William Peter Blatty to write his 1971 bestseller, "The Exorcist," which led to the movie in 1973. Blatty's story featured a 12-year-old girl played by Linda Blair.|publisher =The Washington Post|accessdate = 2007-12-31}}</ref> Rev. William Van Roo, third Jesuit priest, was also there to assist Rev. Bowdern in casting out the [[unclean spirit]]s from Mannheim.<ref name="Washington Post">{{cite web|url = https://www.washingtonpost.com/wp-dyn/articles/A18767-2005Mar8.html|title =Jesuit Priest Walter Halloran|quote= Father Halloran was the last living Jesuit who assisted in the exorcism in 1949 at a psychiatric unit in St. Louis. Father Halloran was a 27-year-old Jesuit scholastic at St. Louis University when a priest called him to the psychiatric wing at Alexian Brothers hospital. The Rev. William S. Bowdern was trying to help a 14-year-old boy from Mount Rainier who he believed was possessed by a demon, and he needed a strong man to help control the boy. A third Jesuit, the Rev. William Van Roo, also was there. "The little boy would go into a seizure and get quite violent," Father Halloran told the St. Louis Post-Dispatch in 1988. "So Father Bowdern asked me to hold him. Yes, he did break my nose." Father Halloran said he saw streaks and arrows and such words as "hell" on the boy's skin. Father Halloran told a reporter that the boy went on to lead "a rather ordinary life." A news account of the incident inspired William Peter Blatty to write his 1971 bestseller, "The Exorcist," which led to the movie in 1973. Blatty's story featured a 12-year-old girl played by Linda Blair.|publisher =The Washington Post|accessdate = 2007-12-31}}</ref> During the exorcism, Ronald spat in the eyes of the pastors, despite the fact that his eyes were closed.<ref name="Sue Lim - Thook">{{cite book|url =https://books.google.com/books?id=_ZH_CdJpxoUC&pg=PA98&dq=Phyllis+Mannheim&lr=&cd=2#v=onepage&q=Phyllis%20Mannheim&f=false|title= Good Spirits, Bad Spirits: How to Distinguish Between Them|quote= While possessed, Robbie with his eyes closed was able to repeatedly and accurately spit on the faces of those around him. The spirits having the use of their own invisible yes, did not need Robbie's in order to have him spit on those standing around his bed in an attempt to prevent their own eviction from his body.|publisher = Writers Club Press|accessdate = 2010-04-02}}</ref> Rev. Halloran stated that during this scene of [[spiritual warfare]], Ronald's hospital bed shook disturbingly, a vessel of [[holy water]] went soaring through the air, and words such as "[[evil]]" and "[[hell]]", along with other various marks, appeared on the teenager's body.<ref name="Washington Post"/><ref name="Emissary - Observations during Deliverance Ritual">{{cite book|url = https://books.google.com/books?id=q469xc7mbksC&pg=PA69&dq=Walter+Halloran+exorcism+ouija&lr=&cd=13#v=onepage&q=Walter%20Halloran%20exorcism%20ouija&f=false| title = A Faraway Ancient Country|quote=Halloran recalls that the hospital bed began shaking violently as holy water was sprinkled on the youth and that at one point, a bottle of holy water went sailing in mid air, just missing his head. Another vivid memory the Father Halloran has was of the word "evil" appearing on the teen's body during one prayer session, saying that it was a definite word, not some phenomenon up for personal interpretation. The demon, when asked when it would leave, told Bowdern and Halloran that it would only do so when the boy uttered the proper words. At last the teenager said, Christus, Domini or "Christ, Lord." At that moment, the whole hospital echoed with a thunderclap. Then boy told them, "It's over. It's over."|publisher = [[Lulu (company)|Lulu]]|accessdate = 2010-03-27}}</ref> Moreover, Ronald broke Rev. Halloran's nose during the process.<ref name="Washington Post"/> Ronald Hunkeler, while being exorcised, also often shouted in an abnormal tone of voice, which was unlike his normal tone of voice.<ref name="Dr. Mehra Shrikhande - Voice">{{cite book|url = https://books.google.com/books?id=SpeXY898fkYC&pg=PA129&dq=Luther+Miles+Schulze&cd=4#v=onepage&q=Luther%20Miles%20Schulze&f=false|title = Paranormal Experiences |quote= During such times the boy would tremble violently and shout in a voice that was not in anyway like his normal one.|publisher =Unicorn Books|accessdate = 20107-04-04}}</ref> In total, the [[Roman Ritual|exorcism ritual]] to cast out demons from the boy's body were performed thirty times over a period of two months.<ref name="Dr. Mehra Shrikhande - Duration">{{cite book|url = https://books.google.com/books?id=SpeXY898fkYC&pg=PA129&dq=Luther+Miles+Schulze&cd=4#v=onepage&q=Luther%20Miles%20Schulze&f=false|title = Paranormal Experiences |quote= Finally, Father William Bowdern stayed with the boy for two months and performed the ritual of exorcism thirty times. |publisher =Unicorn Books|accessdate = 20107-04-04}}</ref> On 10 March 1949, Fr. Bowdern wrote in his private diary that "Hunkeler entered a trance-like state as 14 witnesses watched during one of his exorcisms."<ref name="Yang2021"/> The clerics, asked the demons when they would flee, who responded to Rev. Bowdern and Rev. Halloran that they would depart when the Ronald uttered the proper words.<ref name="Emissary - Observations during Deliverance Ritual">{{cite book|url = https://books.google.com/books?id=q469xc7mbksC&pg=PA69&dq=Walter+Halloran+exorcism+ouija&lr=&cd=13#v=onepage&q=Walter%20Halloran%20exorcism%20ouija&f=false| title = A Faraway Ancient Country|quote=Halloran recalls that the hospital bed began shaking violently as holy water was sprinkled on the youth and that at one point, a bottle of holy water went sailing in mid air, just missing his head. Another vivid memory the Father Halloran has was of the word "evil" appearing on the teen's body during one prayer session, saying that it was a definite word, not some phenomenon up for personal interpretation. The demon, when asked when it would leave, told Bowdern and Halloran that it would only do so when the boy uttered the proper words. At last the teenager said, Christus, Domini or "Christ, Lord." At that moment, the whole hospital echoed with a thunderclap. Then boy told them, "It's over. It's over."|publisher = [[Lulu (company)|Lulu]]|accessdate = 2010-03-27}}</ref> Eventually, Ronald Hunkeler said "Christus, Domini" or "Christ, Lord."<ref name="Emissary - Observations during Deliverance Ritual"/> When these words were spoken, there were reports of a loud noise, noted as a "thunderclap" or "shotgun" throughout the floors of the hospital.<ref name="Emissary - Observations during Deliverance Ritual"/><ref name="Terry D. Cooper, Cindy K. Epperson - Awaaz at Conclusion">{{cite book|url =https://books.google.com/books?id=DXHqjYs3l5kC&pg=PA25&dq=Robbie++exorcism&lr=&cd=1#v=onepage&q=Robbie%20%20exorcism&f=false|title= Evil: Satan, Sin, and Psychology |quote= When the exorcism was completed, there were reports of a very loud noise, like a shotgun going off, throughout the hospital. Even people who had no idea that an exorcism was occurring on the fifth floor reported the noise. After the exorcism was finished, the room was shut off and sealed so that no one would reenter it.|publisher = [[Paulist Press]]|accessdate = 2010-04-02}}</ref> After this pandemonium, Ronald Hunkeler declared "It's over. It's over."<ref name="Emissary - Observations during Deliverance Ritual"/> The room of Alexian Brothers Hospital in which the deliverance was performed was then sealed off in order that none would be able to reenter that area.<ref name="Terry D. Cooper, Cindy K. Epperson - Awaaz at Conclusion">{{cite book|url =https://books.google.com/books?id=DXHqjYs3l5kC&pg=PA25&dq=Robbie++exorcism&lr=&cd=1#v=onepage&q=Robbie%20%20exorcism&f=false|title= Evil: Satan, Sin, and Psychology |quote= When the exorcism was completed, there were reports of a very loud noise, like a shotgun going off, throughout the hospital. Even people who had no idea that an exorcism was occurring on the fifth floor reported the noise. After the exorcism was finished, the room was shut off and sealed so that no one would reenter it.|publisher = [[Paulist Press]]|accessdate = 2010-04-02}}</ref><ref>{{cite web |title=Inspiration for the movie 'The Exorcist' has been identified as former NASA engineer |url=https://nationalpost.com/news/world/inspiration-for-the-movie-the-exorcist-has-been-identified-as-former-nasa-engineer |publisher=[[National Post]] |language=English |date=December 22, 2021}}</ref>
== Later life ==