Eyler attended St. Joseph School in Lebanon, Indiana. Although tall for his age and active in sporting activities, he was regularly targeted by bullies due to his being from a poor family and his parents' divorce, frequently leading to his sister, Theresa, confronting her brother's tormentors. Eyler was viewed by teachers as a quiet yet likable pupil, with few friends. Due to his increasing stubbornness and erratic behavior, Eyler's mother placed him in a home for unruly boys in 1963. He found this experience emotionally devastating, and within weeks had tearfully persuaded his mother to allow him to return home. Shortly thereafter, Eyler underwent psychological tests which revealed him to be of average intelligence, although suffering from severe insecurity and holding an extreme fear of separation and abandonment. Deducing these fears sourced from his home life, staff recommended Eyler be temporarily placed in a Catholic boys' home in Fort Wayne. He remained at this residence for six months before he returned to the care of his mother.
