Kenneth Allen McDuff grew up in Rosebud, a small town in central Texas, on 201 Linden Street. He was the fifth of six children born to John Allen "JA" and Addie McDuff. His father ran a successful concrete business during the construction boom in Texas in the 1960s. McDuff's family, especially his mother Addie, indulged him. Addie, often called the "pistol-packing mama," once threatened a school bus driver with a gun after the driver kicked McDuff's twin brother, Lonnie, off the bus.

In high school, McDuff gained a reputation as a bully. He often picked on weaker students, especially after losing a fight with Tommy Sammons, a popular and athletic boy. This loss embarrassed McDuff and led him to quit school. After dropping out, he worked for his father's business, doing manual labor. McDuff would later boast that elderly women admired his lawn-mowing skills, which made others envious. He was also convicted of several burglaries and sent to prison.

Kenneth McDuff's criminal activities began early in his life. At just 18 years old, in 1964, he was convicted of 12 counts of burglary and attempted burglary across three Texas counties. He was sentenced to serve 12 four-year prison terms concurrently but was released on parole in December 1965. Despite his early release, McDuff briefly returned to prison after getting into a fight. It was during this period that his accomplice, Roy Dale Green, revealed McDuff's boastful claims of having raped and killed two young women, though he hadn't yet been convicted of murder.

On August 6, 1966, McDuff and Green spent the day working before cruising around, as McDuff was on the lookout for a girl. That evening, they spotted Robert Brand, his girlfriend Edna Sullivan, and Robert's cousin Mark Dunman by their parked car. McDuff, armed with a .38 Colt revolver, forced them into the trunk of their car. 

He drove them to a remote field where he executed Brand and Dunman by shooting them in the trunk. Sullivan was transferred to McDuff's car, where she was repeatedly raped by both McDuff and Green. Ultimately, McDuff strangled Sullivan with a broomstick before discarding her body in the bushes.

Despite receiving a death sentence for these brutal crimes, McDuff's sentence was commuted to life in prison. He managed to secure parole in 1989, and within days of his release, he resumed his murderous ways. His subsequent victims included Sarafia Parker, Brenda Thompson, Regenia DeAnne Moore, Colleen Reed, Valencia Joshua, and Melissa Northrup, among others. McDuff's reign of terror spread across multiple Texas counties, complicating the investigation.

He was finally apprehended in May 1992 in Kansas City after a coworker recognized him from America's Most Wanted. McDuff's arrest brought an end to his horrifying spree, but the justice system had to catch up with his heinous acts. 

He was convicted of capital murder for the killing of Melissa Northrup and sentenced to death on February 18, 1993. After several appeals, his execution was carried out on November 17, 1998. McDuff was buried in the Captain Joe Byrd Cemetery in Huntsville, Texas, marked by a simple headstone bearing only the date of his execution and his death row number.