SIOUX FALLS, S.D. (AP) - An investigation has determined that a man serving life in prison for the deaths of his wife and son apparently committed suicide, according to the attorney general's office.

Brian Leingang, 34, was found unresponsive in his penitentiary cell on June 17. Attempts to revive him failed, the state Department of Corrections said.

Last February, a jury in Sioux Falls found Leingang guilty but mentally ill in the deaths of his wife, Melissa Leingang, and their infant son, Caden. The couple earlier lived in Mandan, N.D.

The state Division of Criminal Investigation, which investigates all inmate deaths, has concluded its investigation into Leingang's death.