Born in Freeburg, Ill., on May 11, 1929, he was one of eight children of Albert J. and Katherine E. Koesterer. He entered the Society of Jesus (Jesuits) Aug. 8, 1951, at St. Stanislaus Seminary in Florissant. He pronounced first vows Aug. 15, 1953, and was ordained a priest June 16, 1964, at St. Mary’s College in St. Marys, Kansas. He pronounced final vows Feb. 1, 1972, at De Smet Jesuit High School in St. Louis.

Father Koesterer earned a bachelor of arts in philosophy and a master’s degree in German at Saint Louis University. He studied theology at St. Mary’s College in Kansas.

Father Koesterer taught German and English at Saint Louis University High School for two years, 1959-61. In 1967, he was assigned to teach German and French at De Smet Jesuit, where he remained for nine years. In 1976, he shifted his apostolic work and dedicated the next four years to studying music; he earned a master’s degree in piano from Ball State University in 1979.

Between 1980-89, he served in a variety of parishes in Oklahoma, Colorado and Missouri. He served as a retreat director and spiritual director at White House Retreat in St. Louis from 1991-2006. He served in pastoral ministry in St. Louis from 2006-19, when health issues compelled his move to the infirmary at Jesuit Hall.

Father Koesterer is survived by a brother, Herman Koesterer, of Belleville, Illinois. He donated his body to science.