MANDAN, N.D. — Chad Isaak has pleaded not guilty to charges in connection with a quadruple homicide at a Mandan business in April.

The 45-year-old Washburn chiropractor is accused in the April 1 shooting and stabbing deaths of RJR Maintenance & Management owner Robert Fakler and employees Adam Fuehrer and Bill and Lois Cobb, who were married.

Isaak was to appear in court Monday for a preliminary hearing and possible arraignment, at which he could enter pleas. Defense attorney Rob Quick filed a waiver of appearance and a not guilty plea Thursday, and South Central District Judge Gail Hagerty granted the request Friday morning.

The Monday hearing is canceled. Hagerty set a jury trial for March 2-13 at the Morton County Courthouse in Mandan. Quick was not immediately available Friday morning for comment.

Isaak has been jailed since his April 4 arrest, held on $1 million bond at the Burleigh-Morton Detention Center in Bismarck. He is charged with four counts of murder, punishable by up to life in prison without parole.

He also is charged with felony counts of burglary and concealment within a vehicle and a misdemeanor count of unauthorized use of a vehicle in connection with the homicides at RJR's office near Memorial Highway in Mandan.

Mandan police have not identified a potential motive in the killings. Search warrants and receipts filed in Isaak's case this summer indicate their investigation has swept through Isaak's bank and phone records and his home, office and vehicle, as well as Facebook accounts for the slain.

Police Deputy Chief Lori Flaten last week declined to answer questions about the case, citing prosecutors.

"They don't want us discussing anything about it. That's per them," Flaten said. "They just would rather we not talk about anything."

Morton County prosecutor Gabrielle Goter was not immediately available for comment.