Dr. Hans Holzer, PhD, was one of the early American writers to play a prominent role in the spread of contemporary witchcraft, Wicca, and paganism during the late 1960s and early 1970s. A prolific writer of over 145 books, mainly on associated occult, paranormal, and supernatural subjects, his early books on witchcraft, namely The Truth About Witchcraft (1969), The New Pagans: An Inside Report on the Mystery Cults of Today (1972) and Inside Witchcraft (1980), were written when few other books on witchcraft were available. As such, he did much to boost and pave the way for many future contemporary writers to follow him.

Holzer is perhaps best known as the famed ghost hunter and paranormal investigator associated with the Amityville horror investigations, which later became the subject of several popular horror films. In January 1977, Holzer, working with the well-known trance medium Ethel Johnson-Meyers, entered 112 Ocean Avenue in Amityville, New York. In 1974 this had been the place of a horrific crime when the then-occupant Ronald DeFeo, Jr., murdered his own parents and four siblings. After entering the premises, Meyers allegedly made contact the spirit of an old American Indian chief who revealed that the site had once been a sacred Indian burial ground.

During his investigation Holzer discovered bullet holes created during the 1974 murders and took some photos. When developed, they showed some rather unusual anomalies: mysterious halos seemed to hover above them. Holzer believed that Ronald Defeo, Jr., may have been possessed by the old American Indian chief and that unscrupulous property developers had built the house on a sacred Indian burial site - a claim that the Amityville Historical Society strenuously tried to discredit.