William R. Horton was born on August 12, 1951, in Chesterfield, South Carolina. Little is known about his early life, including his childhood and family background. However, he grew up in a time and place that faced challenges typical of many Southern towns during that era.

As a young adult, Horton moved to Massachusetts to seek better opportunities. In the mid-1970s, he became involved in criminal activity, which led to serious consequences. On October 26, 1974, Horton participated in a robbery that ended tragically. He, along with two accomplices, was convicted of murdering a 17-year-old gas station attendant. Following his conviction, Horton was sentenced to life in prison without the possibility of parole. He was placed at the Northeastern Correctional Center in Massachusetts.

During his time in prison, Horton was able to benefit from a furlough program intended for inmate rehabilitation. However, the program had faced criticism and had rules that were debated. Horton received several furloughs while incarcerated.

On October 26, 1974, William R. Horton, along with two accomplices, committed a robbery in Lawrence, Massachusetts. They targeted Joseph Fournier, a 17-year-old gas station attendant. After Fournier cooperated and handed over the money from the cash register, he was fatally stabbed 19 times. Horton and his accomplices disposed of Fournier's body in a trash can, leaving him in a cruel position. Horton was later convicted of murder and sentenced to life imprisonment without the possibility of parole. He was incarcerated in the Northeastern Correctional Center in Massachusetts.

On June 6, 1986, Horton was granted a weekend furlough as part of a prison program. He did not return to prison as required. On April 3, 1987, in Oxon Hill, Maryland, Horton attacked a couple. He pistol-whipped the woman's fiancé, bound and gagged him, and then raped the woman twice. After the assault, he stole the couple’s car. Authorities later apprehended Horton after he was shot during a police pursuit.

On October 20, 1987, a judge sentenced Horton in Maryland to two consecutive life terms plus 85 years. The judge also stated he would not send Horton back to Massachusetts, expressing his concern about the possibility of Horton being released again. As a result, Horton remains incarcerated at Jessup Correctional Institution in Maryland.