BISMARCK, N.D. (AP) — A man accused of killing four people at a North Dakota property management company is challenging search warrants and seeking a change of venue.

Chad Isaak has pleaded not guilty to four counts of murder in the April 1 shooting and stabbing deaths at RJR Maintenance and Management in Mandan.

Isaak, a chiropractor who lived in a mobile home park managed by the agency, argues in a filing Wednesday that authorities did not properly obtain warrants for his home, his truck, his social media accounts and his electronic devices.

Police have not identified a potential motive in the killings. They have said they found spent shell casings, a knife with a bent tip and gun parts in a kitchen freezer at Isaak’s house, all smelling of chlorine bleach.

Isaak in a separate filing asked that his trial be moved from Morton County due to pretrial publicity.