Importance of Bank account statements

Bank account statements are thoroughly examined by K2 during the course of his investigation, as Olesen paid out 250,000 kroner just before his death to unknown parties. Checking bank account statements, K2 discovers that Sara has an unusually large amount of money for a college student, while Kristian refuses to hand over his bank books. As K2 learns, both Sara and Kristian have large amounts of money in their accounts because they were paid by Olesen.