Two ransom deadlines. Days apart. Ransom note indicates knowledge of Nancy and her home. Details no one else would know.
IMO the perp thinks they are smarter than everyone else, and the ransom letter writer is the perp, and they are trying to make it look like a kidnapping for ransom, when most probably it was SA, and the kidnapping ruse is a cover-up, because the perp felt remorse after his crime, and can't get caught because it will cause him further shame and embarrassment. Kind of a "Hey look over there, not here" type scenario.