Gary Randall Muehlberg was born on February 27, 1949, in St. Louis, Missouri. He was the youngest of three children in the Muehlberg family. His parents were William and Christina Muehlberg, who provided a good life for their children. William, a veteran of World War II, served on the Board of Governors in various districts from 1955 to 1957. In 1966, he took a high-paying job at Gulf Oil, leading the family to move to Salina, Kansas.

Gary graduated from high school in 1968. That same year, he and his older brother Ronald were drafted into the Army to serve in the Vietnam War. Gary did not see combat. He was stationed at different military bases in the United States, while Ronald was tragically killed in action on August 21, 1968, during a battle in the Mekong Delta. After finishing his military service, Gary returned to live with his parents. In June 1970, he married his high school girlfriend, and they welcomed their first child shortly after the wedding.

In February 1972, Gary faced legal troubles when he was arrested for allegedly robbing and raping an 18-year-old girl in Salina. The victim reported that he had broken into her home and assaulted her. Muehlberg was ordered to undergo a psychiatric evaluation, where he was determined to be insane. He was convicted of robbery but found not guilty of the rape charge due to his mental state. After spending a month in jail, he was transferred to a veterans' hospital for treatment. He was released in December 1972.

Later that month, Gary was arrested again for assaulting a 14-year-old girl. He had tricked her into letting him inside her home by asking to use the phone. He threatened her with a knife, bound and gagged her, and searched the house for valuables before fleeing when someone approached. He was identified as the assailant and convicted of assault, leading to a five-year prison sentence. His first wife divorced him during this time, and he lost contact with her and their son.

After serving time, Gary enrolled at Central Methodist College and studied psychology. He graduated and attended graduate school at the University of Central Missouri. In 1980, he remarried and had two more children. He worked briefly as a teacher but struggled to keep steady jobs and faced financial difficulties. He drifted from one low-skilled labor job to another, including repairing houses.

By the late 1980s, Gary turned to drug dealing, storing marijuana in his basement. His relationship with his second wife did not last, and they divorced in 1986. He again lost contact with his children. During this time, Gary frequented local fast-food restaurants and began interacting with local prostitutes, becoming known as a manipulative individual in his community. In the early 1990s, he attempted to start a used car business but was unsuccessful.

Gary Randall Muehlberg, known as "The Package Killer," committed a series of murders in and around St. Louis, Missouri, from 1990 to 1993. His first known victim was 18-year-old Robin J. Mihan, who went missing on March 22, 1990. Muehlberg kidnapped her, then assaulted and tortured her for several days in his basement. He ultimately strangled her and disposed of her body along a highway, found tied between two mattresses.

On October 4, 1990, the body of a second victim, 27-year-old Brenda Pruitt, was discovered wrapped in plastic trash bags. The investigation linked this murder to Mihan's through similar binding materials. In June 1991, 40-year-old Donna Reitmeyer's remains were found in a dumpster, also wrapped in bags, showing signs of homicide. Another victim, 21-year-old Sandy Little, was reported missing on September 4, 1990. Her skeletal remains were found in February 1991.

On February 8, 1993, Muehlberg sold a car to 57-year-old Kenneth Atchison, who later went missing. Six weeks after Atchison's disappearance, Muehlberg was implicated when a witness reported he saw Muehlberg with cash right before Atchison vanished. Police found Atchison's body in Muehlberg's basement, handcuffed and showing evidence of torture, asphyxiation, stabbing, and gunshot wounds.

Muehlberg was arrested on March 27, 1993. He admitted to knowing Atchison but denied killing him, blaming another person instead. However, evidence linked him to the crime. In September 1995, he was convicted of Atchison's murder and sentenced to life imprisonment without parole.

In 2008, detectives reopened the cold cases linked to Muehlberg after advancements in DNA technology. In March 2022, he was identified as the suspect in the murders of Mihan, Pruitt, Reitmeyer, and Little. Following a series of interviews, Muehlberg confessed to these murders, receiving four additional life sentences without parole. As of April 2023, he remains in prison at the Potosi Correctional Center.