Rardon's father, William Harley Rardon, served as a master sergeant in the U.S. Air Force. Rardon mentioned that his parents were good to him. Reflecting on the murders, Rardon stated, "I had a perfect family. Almost too perfect. My father never drank, never cheated, and never neglected us. His only vice was smoking. My mother was also faultless. Yet, at times, I felt like I couldn't meet their expectations."

On July 7, 1962, 23-year-old James Homer Smith, a former Marine, was at a train station in Indianapolis looking for someone to give a ride east. Thomas Rardon, then 19 and an AWOL sailor, accepted the offer. Later that day, Rardon shot Smith twice in the head and hid his body in Smith's car. Smith's body was discovered 12 days later in Washington, Pennsylvania. Rardon was arrested on December 5, 1962, and charged with first-degree murder. He claimed self-defense, alleging that Smith had made sexual advances towards him. 

On April 19, 1963, Rardon pleaded guilty to voluntary manslaughter and received a sentence of 2 to 21 years in prison. His father, who visited him regularly in prison, died of a heart attack on January 8, 1966. Rardon's grandfather, who had briefly cared for him as a child, visited him in prison and told him his father had died of a broken heart, a statement that Rardon said he never forgot.

In 1965, a psychiatrist labeled Rardon as "near psychotic" and "very dangerous." However, two years later, the same psychiatrist re-evaluated Rardon and deemed him minimally likely to be violent again. After his initial psychiatric evaluation, Rardon worked as a medical records keeper for the psychiatrist. Rardon was released on parole on May 8, 1967. In 1969, he was sentenced to 3 to 5 years in prison for robbery in Connecticut.

After serving his time, Rardon divorced his first wife, remarried, and secured a machinist job earning nearly $250 a week. However, he became bored, quit his job, and left his wife. As bills piled up, he found a shotgun that belonged to his father-in-law and sawed off the barrel. From November 14 to November 18, 1974, Rardon killed three men in Chicago with the sawed-off shotgun during robberies.

On November 14, 28-year-old Gene R. Ravenscraft was working overtime in his office when Rardon entered and shot him, taking $23 and Ravenscraft's coat. On November 16, 31-year-old cab driver Herbert Noakes was shot by Rardon, who stole $63 from him. Noakes was killed a week before his planned marriage. On November 18, 50-year-old Asher Gruenberg was shot in his office by Rardon, who stole his wallet and used his credit card multiple times. The FBI tracked Rardon to a Sears store in Louisville, Kentucky, and arrested him on January 16, 1975. He confessed to all three murders.

Rardon was charged with three counts of murder and three counts of armed robbery in Illinois. He also faced federal charges for transporting a stolen vehicle and possessing an unregistered firearm. In 1976, he pleaded guilty to the federal charges and received a 12-year prison sentence. On February 17, 1977, he pleaded guilty to the state charges and was sentenced to three concurrent 40 to 100 years terms, to run consecutively with his federal sentence. The judge remarked that he had never seen a case as severe. The prosecution highlighted the minimal monetary value of the lives lost, and Rardon himself admitted he deserved to die.

While in prison, Rardon learned computer skills, received a cooking certificate, and took college business courses. He was eligible for parole in 1987 but was denied at all hearings. His projected discharge date was September 30, 2016. In a 2012 parole hearing, Rardon expressed remorse and outlined his plans for life after release, which included relying on his elderly relatives for support. The Illinois Prisoner Review Board acknowledged his good behavior but concluded that his crimes were too severe for remorse to be sufficient.

Rardon completed his state sentence on September 30, 2016, and was transferred to federal custody to serve his 12-year sentence. He was released from federal prison on December 17, 2020, having served nearly 50 years in total for the murders. Rardon died in Indiana in 2024.