William Kenneth Wagner was born on February 18, 1903, in Scott County, Virginia. He grew up in a rural area, where life was often tough. Not much is detailed about his early family life, but when he was just fourteen years old, he decided to leave home. Instead of staying in school or working a regular job, he joined a circus. 

Wagner became known as a trickshot artist in the circus. His skills made him stand out, as he learned to shoot accurately and perform tricks that entertained many people. As he grew older, the United States faced the start of Prohibition. During this time, alcohol was illegal, and many people turned to making their own drinks. Wagner got involved in this by making and selling moonshine. He was a large man, standing six feet three inches tall and weighing 260 pounds. 

William Kenneth Wagner's criminal activities began with his arrest in 1925 for stealing a watch in Lucedale, Mississippi. While awaiting trial, he overpowered the jailer and escaped on a stolen horse. This led to a violent encounter where he shot his way out of a trap set by local lawmen, killing a deputy in the process. He continued his escape, engaging in a shootout with law enforcement in Tennessee, which resulted in two more deaths. Following a series of confrontations, he surrendered to a storekeeper in Waycross, Virginia.

After a trial in Sullivan County, Wagner was sentenced to death, but he managed to escape from jail temporarily before executing a successful prison break. He fled to Mexico, where he committed several robberies. Eventually, he returned to the United States and killed two unarmed men, Will and Sam Carper, at a home in Arkansas. This led to his surrender to Sheriff Lillie Barber, who later fell in love with him and refused to put him on trial due to the nature of the charges.

Wagner was tried in Mississippi for the murder of the Carper brothers. In 1926, he received a life sentence at Parchman Farm. He attempted to escape several times but was caught again. Notably, he became a trustee in the prison and was responsible for training bloodhounds. He eventually escaped again in 1940 but was found three years later.

His most clever escape took place when he trained the prison dogs not to track him, which allowed him to vanish for years under the alias "Big Jim." He was later placed on the FBI's Ten Most Wanted list. In 1956, he was recaptured after a rival informed the police of his location. After his capture, Wagner expressed relief at returning to Parchman Farm, where he died in 1958.