William Edward Cook Jr. was born on December 23, 1928, in Joplin, Missouri. At the age of five, his mother died unexpectedly, and shortly thereafter, his father abandoned him and his seven siblings in an abandoned mine. The children were discovered by authorities and placed into foster care, but due to a deformed eye and a belligerent attitude, Cook was not adopted and became a ward of the state. He spent his youth in various detention facilities and was eventually incarcerated at the Missouri State Penitentiary. Upon his release in 1950, he expressed a desire to "live by the gun and roam," setting the stage for his subsequent crime spree.

On December 30, 1950, Cook's crime spree began when he kidnapped Lee Archer, an auto mechanic, in Texas. Archer managed to escape, but Cook continued his rampage. On January 2, 1951, he was picked up by the Mosser family—Carl, Thelma, and their three children—while hitchhiking. Over the next three days, he held them hostage, eventually murdering all five family members and their dog, disposing of their bodies in a mine shaft near Joplin, Missouri.

Cook then traveled to California, where he kidnapped Deputy Sheriff Homer Waldrip but later spared his life. Shortly after, he murdered Robert Dewey, a salesman from Seattle, and dumped his body in a ditch. Cook's spree ended when he kidnapped two hunters and forced them to drive him into Mexico. He was apprehended on January 15, 1951, in Santa Rosalia, Mexico, by local police who recognized him. Cook was extradited to the United States, where he was tried and convicted for the murders. He was executed in the gas chamber at San Quentin State Prison on December 12, 1952.