The sudden death of 54-year-old Dan Rivera, who was on tour with Annabelle, said to be the world’s most haunted doll, is being mourned by the paranormal world.

Before he died, Rivera was leading a tour along with other members of the New England Society for Psychic Research. The tour included going around US to show off the haunted doll.

Dan Rivera -- the paranormal investigator who worked for the Annabelle haunted doll tour -- told people around him he wasn't feeling well just hours before his untimely death in Pennsylvania ... TMZ has learned.