BISMARCK, N.D.—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 1st shooting and stabbing deaths at RJR Maintenance and Management in Mandan, North Dakota.

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.