Kelsey Patterson was born on March 24, 1954, in Anderson County, Texas. He grew up in a small area and faced various challenges during his childhood. Details about his family life are limited, but it is known that he had a close connection with his grandmother, who was his primary caretaker. After her death, Patterson's mental health began to decline.

In 1981, he was diagnosed with paranoid schizophrenia. This mental illness affected his thoughts and actions throughout his life. Friends and family noticed changes in him after he lost his grandmother, which marked the beginning of his struggles with mental health.

On August 25, 1992, Patterson told his roommate that he might not ever see him again. He expressed some troubling thoughts that day. Later, he walked outside and fired a .38 caliber pistol into an aluminum pan. 

On August 25, 1992, in Palestine, Texas, Kelsey Patterson committed two murders. He started his day by stepping into his front yard with a .38 caliber pistol. He fired the gun into an aluminum pan three times. Then, he walked to Oates Oil Company, where he found 63-year-old Louis Oates standing on the loading dock. Patterson approached Oates from behind and shot him in the back of the head. He left the scene but returned shortly after to shoot Dorothy Harris, Oates's 41-year-old secretary, who had come outside after hearing the initial shots.

After the attacks, Patterson went to a friend's house, stripped off his clothes, and was later arrested while standing naked in the street. The motive for the murders was unclear. However, a friend of Louis Oates mentioned that there had been an argument between Patterson and Oates about who was the better football player years prior.

At Patterson's trial, two men testified that Patterson had shot them in separate incidents in the early 1980s, resulting in serious injuries. Defense attorneys claimed that Patterson suffered from mental health issues. His half-sister said his problems began after the death of their grandmother, who had been his primary caretaker. The prosecution argued that Patterson, although violent, was not insane. After deliberating for two hours, the jury found him guilty on July 1, 1993, and sentenced him to death after four additional hours of discussion.

In May 2004, the Texas Board of Pardons and Paroles recommended changing Patterson's death sentence to life imprisonment due to his mental illness. However, Governor Rick Perry denied this request, stating that Patterson was a dangerous individual. Texas had no life without parole option at that time, meaning that life sentences could potentially lead to parole after 40 years. In response to Patterson's execution, Texas changed its laws regarding capital punishment in 2005.

Kelsey Patterson was executed by lethal injection on May 18, 2004, at the age of 50. He did not request a last meal but accepted a candy bar and a soft drink offered to him. During his execution, he expressed his belief that he was not guilty of capital murder and repeatedly asked for his rights. As the lethal drugs were administered, he muttered for his life back. After his execution, Patterson was buried at Captain Joe Byrd Cemetery.