The 54-year-old paranormal investigator died while on his sold-out 'Devils on the Run' tour.
A well known figure in paranormal circles, Rivera had previously appeared in the Travel Channel's Most Haunted Places and served as producer for Netflix's 28 Days Haunted.
His most recent role had been with the Devils on the Run tour that saw him, along with other members of the New England Society for Psychic Research (NESPR), travel around the United States with Annabelle - the infamous haunted doll that inspired some of The Conjuring movies.
He had just finished a three-day sell-out stop in Gettysburg when he was found unresponsive in his hotel room, prompting a call to the emergency services.
Despite the best efforts of paramedics, they were unable to revive him.
According to the coroner's office, his death did not appear to be suspicious, although right now it remains unclear exactly what happened.
His close association with the Annabelle doll has since prompted a great deal of speculation over whether this might have had something to do with it.
The doll itself has been a magnet for paranormal activity since the 1970s when Ed and Lorraine Warren claimed to have witnessed it physically moving.
It has also been associated with disturbing and malicious behavior.
In reality, however, it is extremely unlikely that the doll had anything at all to do with Rivera's death.