MONSTER DEAD: Notorious Serial Killer Joseph Duncan — Who Slaughtered an Idaho Family and Tortured Children on Camera — Dies of Brain Cancer on Death Row

Terre Haute, Indiana — July 3, 2026

The man many called pure evil is finally gone.

Joseph Edward Duncan III, the convicted serial killer and child molester who unleashed unimaginable horror on multiple families across the Pacific Northwest and California, died Sunday at age 58 from stage 4 brain cancer while awaiting execution on federal death row.

Officials at the Terre Haute Federal Correctional Institution confirmed his death, ending decades of pain for the survivors and families he destroyed.

Duncan’s reign of terror peaked in May 2005 when he slaughtered Brenda Groene, her 13-year-old son Slade, and her boyfriend Mark McKenzie at their home near Coeur d’Alene, Idaho. He then kidnapped Brenda’s young children — 9-year-old Dylan and 8-year-old Shasta — took them deep into the Montana wilderness, and subjected them to horrific torture that he recorded on video. Dylan was murdered; Shasta was eventually rescued alive from a Denny’s restaurant.

Duncan had already left a trail of devastation before that: He was linked to the 1997 abduction and murder of 10-year-old Anthony Martinez in California, and he later admitted to killing two young sisters in Washington state in 1996.

A jury sentenced him to death in 2008 for the federal crimes against the Groene children. He also received life sentences in other cases.

But it was cancer — not the execution chamber — that ultimately claimed him.

For the families who waited years for justice, the news brought a bittersweet wave of relief.

Anthony Martinez’s mother, Diana, said: “The sun is brighter today, and my soul is lighter. The world is a more beautiful place without the evil that is Joseph Duncan. God chose to make his end a long suffering and I believe that is fitting.”

Anthony’s father, Ernesto, added: “While I would’ve liked to witness his execution, knowing he is now standing before God being held accountable… that’s the real justice.”

Acting U.S. Attorney Rafael M. Gonzalez Jr. spoke for many when he said: “While his death will not bring back the lives cut so tragically short, perhaps death will now allow space for some degree of healing, peace, and closure.”

Duncan had been diagnosed with terminal glioblastoma and declined aggressive treatment. He spent his final months on death row, a place where he once claimed everyone would be “better off” if executed.

For the survivors and the communities scarred by his crimes — from the Groene family billboard campaigns to the investigators haunted by the torture videos he created — his passing marks the end of a long nightmare.

A monster is gone. The healing, for those he left behind, continues.