He went on to study archaeology and ancient history at the University of Vienna but as the family was Jewish, they decided it was unsafe to stay in Austria and left the country for New York City in 1938.

[5] His extensive involvement in researching the supernatural included investigating The Amityville Horror and some of the most prominent haunted locations around the world.

In January 1977, Holzer and spiritual medium Ethel Meyers entered 112 Ocean Avenue in Amityville, New York.

Meyers claimed that the house had been built over an ancient Native American burial ground and the angry spirit of a Shinnecock Indian Chief, "Rolling Thunder", had possessed the previous occupant, Ronald Defeo Jr., driving him to murder his family.

[9] Photographs taken at the scene revealed curious anomalies such as the halos which appeared in the supposed images of bullet marks made in the original 1974 murders.

[17] His book Patterns of Destiny from 1975 appeared as a noticeable prop in the movie Flatliners, standing next to the framed photograph of Julia Roberts character's dead father.

Skeptical investigator Joe Nickell has written that Holzer did not provide verification for some of his claims and he credulously accepted spirit photographs, anecdotal reports, and other doubtful evidence.

[18] Nickell also wrote that the mediums Holzer endorsed, Ethel Meyers and Sybil Leek, offered "unsubstantiated, even unverifiable claims, or information that can be gleaned from research sources or from knowledgeable persons by “cold reading” (an artful method of fishing for information).