Wolf Hour by Jo Nesbo

From the modern master of Nordic noir comes a shocking new thriller set in contemporary Minneapolis, in which a detective and a crime writer conduct parallel investigations, six years apart, into a series of puzzling murders.
Minneapolis, Minnesota, 2016. When a small-time criminal and gun dealer is shot down in the street, all signs point to Tomas Gomez, a quiet man with a mysterious past—and deep connections to a notorious gang—who has seemingly vanished into thin air. Other murders soon follow, and it appears Gomez is only getting started. Meanwhile, Bob Oz, a down-and-out suspended police officer with a dubious past of his own, becomes fascinated by the case: he is obsessed with the notion of hunting down a serial killer who only he can understand, a killer with a story as tragic as his own.
Minneapolis, Minnesota, 2022. An enigmatic Norwegian man with ties to Minneapolis—a self-described crime writer—has traveled to the United States to research the Gomez case, in the hopes of writing a book about it. But as his investigation progresses, the writer’s seemingly neutral position reveals itself to be more complicated than the reader is initially led to believe.