Question: How old was the boy that William S. Bowdern performed an exorcism on?

Context paragraphs:
Exorcism of Roland Doe: In the late 1940s, in the United States, priests of the Roman Catholic Church performed a series of exorcisms on an anonymous boy, documented under the pseudonym "Roland Doe" or "Robbie Mannheim".  The 14-year-old boy (born circa 1935), was the alleged victim of demonic possession, and the events were recorded by the attending priest, Raymond Bishop.  Subsequent supernatural claims surrounding the events were used as elements along with the Loudun possessions in the 1971 novel "The Exorcist" by William Peter Blatty and the 1973 film adaptation.

The Exorcism of Emily Rose: The Exorcism of Emily Rose is a 2005 American legal drama horror film directed by Scott Derrickson and starring Laura Linney and Tom Wilkinson.  The film is loosely based on the story of Anneliese Michel and follows a self-proclaimed agnostic who acts as defense counsel (Linney) representing a parish priest (Wilkinson), accused by the state of negligent homicide after he performed an exorcism.

The Exorcist (film): The Exorcist is a 1973 American supernatural horror film, adapted by William Peter Blatty from his 1971 novel of the same name, and starring Ellen Burstyn, Linda Blair, Max von Sydow, and Jason Miller.  The film is part of "The Exorcist" franchise.  The book, inspired by the 1949 exorcism of Roland Doe, deals with the demonic possession of a 12-year-old girl and her mother's attempts to win back her child through an exorcism conducted by two priests.  The adaptation is relatively faithful to the book, which itself has been commercially successful (earning a place on "The New York Times" Best Seller list).

William S. Bowdern: Father William S. Bowdern, S.J. (February 13, 1897 - April 25, 1983) was a Catholic priest of the Society of Jesus in St. Louis, Missouri, United States.  He was the author of "The Problems of Courtship and Marriage" printed by "Our Sunday Visitor" in 1939.  He was a graduate of and taught at St. Louis University High School; he also taught at St. Louis University.  Bowdern participated in an exorcism of Roland Doe in 1949.  The incident became the basis of William Peter Blatty's novel, "The Exorcist".

Mehandipur Balaji Temple: Mehandipur Balaji Mandir (Hindi/Rajastani: मेहंदीपुर बालाजी मंदिर) is a noted Hindu temple, mandir in Dausa district of Rajasthan, dedicated to the Hindu God Hanuman.  The name "Balaji" is applied to Shri Hanuman in several parts of India because the childhood ("Bala" in Hindi or Sanskrit) form of the Lord is especially celebrated there.  The temple is dedicated to Balaji (another name for Shree Hanuman Ji).  Unlike similar religious sites it is located in a town rather than the countryside.  Its reputation for ritualistic healing and exorcism of evil spirits attracts many pilgrims from Rajasthan and elsewhere.  The old village Mehandipur is located nearby the small hill.  Old village is not well developed.

Raymond J. Bishop: Raymond J. Bishop (January 15, 1906 – February 1978) was a Roman Catholic priest.  He became one of the several priests involved in the case of exorcizing a boy in St. Louis, Missouri, who was allegedly possessed after using a Ouija board.  The case would inspire author William Peter Blatty to write a novel about exorcism, titled "The Exorcist".

Exorcising a boy possessed by a demon: The exorcism of a boy possessed by a demon, or a boy with a mute spirit, is one of the miracles attributed to Jesus reported in the synoptic Gospels, involving the healing of a demonically possessed boy through exorcism.  The account appears first in the Gospel of Mark and is repeated, slightly amended, in the Gospels of Matthew and Luke.  In the Gospel narratives, this healing takes place following the Transfiguration.

Puritan exorcism: Puritan exorcism was the use of exorcism by Puritan ministers.  The demonology of Puritans was not unusual within the Early Modern demonology of Protestants; but the use of ritual and prayer in exorcism was more distinctive.  The Church of England did not recognise the ritual of exorcism, while the Roman Catholic Church has always done so.  Some radical Puritan ministers performed exorcisms; but some leading Puritan writers, such as William Perkins, opposed the ritual, while accepting the underlying theories, for example about witchcraft.

Damien Karras: In William Peter Blatty's "The Exorcist", Father Karras was one of the priests who exorcises the demon from young Regan MacNeil.  He is a Jesuit psychiatrist suffering a crisis of faith.  He searches for proof to lead an exorcism, yet during his investigation he comes to realize that there is no better way for God to prove His own existence than to reveal the foul presence of a demon.  During the exorcism, the demon frequently brings up the subject of Karras's mother's death and how he wasn't there to see her die, which seems to trouble Karras emotionally.

Walter Halloran: Walter H. Halloran SJ (September 21, 1921 – March 1, 2005) was a Catholic priest of the Society of Jesus who, at the age of twenty-six, assisted in the exorcism of Roland Doe, a thirteen-year-old Lutheran boy in Cottage City, Maryland, who was allegedly possessed.  The case inspired William Peter Blatty to write his novel "The Exorcist".

Supporting paragraphs: William S. Bowdern Exorcism of Roland Doe
Answer: 14-year-old