Authorities in North Dakota have arrested a suspect accused of killing four people Monday morning at a property management business in Mandan.

The Associated Press reports that Chad Isaak, 44, was arrested on Thursday and is due in court on Friday where he is expected to be formally charged in the multiple homicide.

Isaak is a chiropractor who was reportedly living at a mobile home park operated by RJR Maintenance and Management, which was the site of a mysterious killing on Monday morning. The victims have been identified as Robert Fakler, 52, RYR’s owner; Lois Cobb, 45; her husband, Bill Cobb, 50; and Adam Fuehrer, 42; all employees of RJR Maintenance.

While police refused to reveal the cause of death in the immediate days following the multiple homicide, authorities have now said that all of the victims were shot or stabbed, in some cases both, suggesting that the killer used multiple murder weapons. It is unclear if authorities have recovered any of the weapons, and a motive remains unknown.

According to the Associated Press, Isaak was a tenant at a mobile home park in Washburn, which is about 35 miles outside of Mandan, that RJR managed. The suspect has no criminal history, and reportedly owns a chiropractic business. Previously, he was a lab technician for the U.S. Navy.

Rolf Eggers, who owns the mobile home park, told the Associated Press that he never personally meet Isaak and that the tenant had never been the source of any issues in the past — for him, or for Fakler, who he said he spoke to on a regular basis.

“He was a non-issue,” Eggers said. “He never attracted any attention.”

Isaak appears to be the only person of interest in the investigation, as authorities have said they are not seeking additional suspects.

[Feature image: Chad Isaak/North Dakota Statewide Automated Victim Information and Notification Program via AP]