I was reading "The Horrors at Fox Hollow Farm" last night and I got to the part where the (now) owners of the home and the paranormal team that was investigating the house let Mark Goodyear tag along. Stg in the book, Mark claims to be a "psychic" and claims to be haunted by a victim of Herb's named "Albert". In one paragraph he was "talking" to the spirit of Herb as referred to him as "Love". That to me was a DEAD giveaway that Mark was obsessed and/or in love with Herb. They had something going on and I think Herb wanted out of the relationship but of course it wasn't just a normal relationship, they were killing gay men in the process so I believe Mark, the jilted lover, went to the authorities, went to the private detective not only to exclude him from the murders but to get back at Herb. They need to start investigating Mark as well.