Village Heresy by Don Marshall

After some arm-twisting, a reluctant Kale gives testimony as to how he found God to a group of Bible study friends. The confessional exposes youthful experiences of dabbling in the occult and reveals the desire to revive a long-dormant writing career. The disclosures bring to light a novel in progress, detailing a personal role in a decades-old mass murder ordered by the demon Zozo.
The revelations summon the demon, who proceeds to wreck the lives of the group members by exposing their undisclosed sins. As their relationships unravel, seemingly chance encounters funnel Kale closer to confronting the consequences of his youth.
The path of a sadistic serial killer terrorizing the Pacific Northwest intersects with the group of friends. Each must face their own transgressions as the killer moves closer and unveils a dark connection to the group. Kale’s path to redemption and the only way to make things right require making the ultimate sacrifice.