Joseph E. Duncan III

Joseph Edward Duncan III (February 25, 1963 – March 28, 2021) was an American convicted serial killer and child molester. He was on death row in federal prison for the 2005 kidnappings and murders of members of the Groene family of Coeur d'Alene, Idaho.
He was also serving 11 consecutive sentences of life without parole for the Groene muders and the 1997 murder of Anthony Martinez of Beaumont, California. 
Duncan confessed to — but has not been charged with — the 1996 murder of two girls, Sammiejo White and Carmen Cubias, in Seattle. At the time of the attack on the Groene family, Duncan was on the run from a child molestation charge in Minnesota. He spotted Shasta and Dylan Groene playing outside as he drove past their house on Interstate 90.
In October 2020, Duncan was diagnosed with terminal glioblastoma and had brain surgery. He died on March 28, 2021 in prison in Terre Haute, Indiana from the illness, aged 58.