Mad River by John Sandford

They thought they were Bonnie and Clyde. And what's-his-name, the sidekick. Three teenagers with dead-end lives, chips on their shoulders, and guns. The first person they killed was a woman during a robbery. The second was incidental. Simply in the way. Then? Hell, why not keep on going?

It's not until Bureau of Criminal Apprehension investigator Virgil Flowers steps into the Shinder murder scene that the clues begin to come together. As the crime spree cuts a swath through rural Minnesota, a growing army of cops join Virgil in trying to track the teenagers down. But even Virgil doesn't realize what's about to happen.