MANDAN, N.D. (Prairie Public Radio) – A man convicted of multiple homicide in Mandan is dead.

North Dakota’s Department of Corrections say 48 year-old Chad Isaak died of “self-harm.”

A release from the North Dakota Highway Patrol said the Patrol was called to the state Penitentiary in Bismarck at 5:44 pm Sunday, regarding a “resident who had caused self-harm.” Isaak was taken to Sanford Hospital, where he was pronounced dead at 6:24 pm.

No further information has been released, pending an investigation.

Isaak was convicted of killing four employees of RJR Management at its Mandan office in April 2019. He was sentenced to four life terms without parole and had appealed those convictions to the North Dakota Supreme Court.