My inspirations are:
The Manson Murders

James Ellroy’s Blood’s A Rover

Anton LeVay’s Magic Circle

The collective amphetamine psychosis of US government officials in that era

The Hounds of Tindalos 

The CIA drug magician (probably a result of amphetamine psychosis)

William S. Burroughs

Hunter S. Thompson

Kenneth Anger

With some other mythos mixed in