The co-owner of a North Dakota business where four people including her husband were slain says she and others don't know why the suspect would target anyone at the company.

Chad Isaak, 44, a chiropractor in Washburn, faces four felony counts of murder in the April 1 deaths of RJR Maintenance and Management co-owner Robert Fakler and three workers in Mandan, a town of 22,000 near the state capital of Bismarck. Isaak lived on property managed by the company, but police have said that while they have plenty of evidence — spent shell casings, a knife and gun parts — they still haven't identified a motive. That was still the case as of Monday, Deputy Chief Lori Flaten said.

Jackie Fakler said RJR officials had few interactions with Isaak, who lived in a mobile home park the company had begun managing just last June. Marketing executive Ben Pace called those few interactions "all very normal."

Fakler said rumors that RJR was raising Isaak's rent or had ordered him to get rid of his dog are false.

"I don't think anything could make sense out of it, no matter what," she said.

Robert Fakler, 52, and employees Adam Fuehrer, 42, and married co-workers Lois Cobb, 45, and William "Bill" Cobb, 50, were shot or stabbed to death before the business opened that Monday. Jackie Fakler said the four victims typically came to work early. It also wasn't uncommon to have an unlocked door while there were workers on the premises.

"This is like home to a lot of people, and it's like being at home and leaving your front door unlocked while you're home," Pace said.

The victims were in different areas of the building and were killed within 13 minutes, according to Fakler. The Cobbs were in the office area; Fakler and Fuehrer in the back shop area.

Police followed evidence from surveillance video at RJR and other businesses to arrest Isaak three days after the slayings. Court documents allege Isaak took one of the company's vehicles, drove about a block, then walked to his own truck parked in the area. Fakler said it wasn't unusual for Bill Cobb to leave a company truck running with the keys in it.

"(Police) got a lot of footage everywhere," she said. "I think they were able to track (Isaak) from here to him leaving town."

After Isaak got back to Washburn, about 35 miles (56 kilometers) north of Mandan, he allegedly went back to work at his chiropractor office. A client of his, Dora Sorenson, has said Isaak "didn't appear any different."

Fakler said, "It doesn't make sense how anybody could walk away, go to work. None of it makes sense."

She and Pace credited police with making a quick arrest but said they are not privy to much more information than the public. Fakler said she's relieved with the arrest "but then now you're flooded with all the questions — why? What could have been so horrible that he had to take four people's lives?"

Isaak remains jailed on $1 million bond. He hasn't responded to interview requests and doesn't yet have an attorney listed to represent him. He could enter pleas at a May 14 hearing.

Isaak could face life without parole if convicted. North Dakota doesn't have the death penalty.

___

Follow Blake Nicholson on Twitter at: http://twitter.com/NicholsonBlake