MANDAN, N.D. (AP) — Police are turning to Facebook and bank records to try to identify a motive for why four people were killed at a North Dakota business two months ago.

Mandan Police Deputy Chief Lori Flaten reports that police are “trying to cover all the bases” in their investigation of the April 1 deaths of RJR Maintenance and Management co-owner Robert Fakler and three workers. Authorities say they were shot and stabbed at the business in Mandan.

Washburn chiropractor Chad Isaak is facing murder charges in the case.

Court documents show police have sought search warrants for Isaak’s personal and business bank records, as well as victims’ Facebook accounts.

Flaten says it’s possible police will never uncover a motive, but wouldn’t comment on how that could affect Isaak’s prosecution.