Clayton was born on September 12, 1955, at the U.S. Army Hospital in Fort Benning, Georgia. He was the oldest of six children. He had one brother and four sisters. Clayton was named after his father, Clayton Raleigh Fountain.

The family moved every one and a half to two years because of his father's military career. His father served in combat tours in Korea and Vietnam. While his father was away and his mother was working, Clayton had to take on many responsibilities at home. 

As the oldest child, Clayton became like a parent to his younger siblings. He had to cook, iron clothes, serve meals, clean the house, and take care of his brother and sisters. He learned to manage these duties from a very young age.

While serving in the Marines in 1974, Clayton was convicted of murdering his staff sergeant in the Philippines. He had stolen and disassembled a pistol from the ship's armory, brought it ashore, and used it to rob a Filipino guard of his shotgun. He then used the shotgun to kill his staff sergeant with a single shot to the chest. Without saying a word, Clayton took five hostages afterward. This incident happened shortly after the staff sergeant had written him up for wearing PT gear in the mess hall.

Clayton was sentenced to life in prison and sent to the United States Penitentiary in Marion, the highest-security prison in the U.S. at the time. While in Marion, he killed three prisoners and a correctional officer with a homemade knife, gaining a reputation as the "Most Dangerous Prisoner" in the federal system. He and another inmate, Hugh Colomb, were convicted of voluntary manslaughter and conveying a weapon in prison, adding 15 years to their sentences. Colomb was released from prison in 2015.

On October 22, 1983, Clayton stabbed correction officer Robert L. Hoffmann to death. This occurred just hours after his friend, Thomas Silverstein, another member of the Aryan Brotherhood, killed another correction officer, Merle Clutts, at the same facility. These murders led to a 23-year lockdown at Marion and helped prompt the creation of the federal supermax prison, United States Penitentiary, Florence ADX.

Clayton was later moved to the United States Medical Center for Federal Prisoners in Springfield, Missouri. He was placed in a specially constructed unit and only allowed contact with authorized personnel. During his twenty years in isolation, he converted to Catholicism and took various theology courses. He earned an associate degree in business, a bachelor's degree in philosophy and business from Ohio University, and a Catholic Catechetical Diploma. He also began a Master of Arts in Religious Studies from Catholic Distance University. Clayton formed connections with an order of Trappist monks and was accepted posthumously as a lay brother after his death from a heart attack in 2004. His life and conversion were chronicled in the book "A Different Kind of Cell: The Story of a Murderer Who Became a Monk," with a foreword by Sister Helen Prejean.