Little is known about the early years of Gary James Lewingdon. He was born on February 14, 1940, in Ohio. He had an older brother named Thaddeus, who was born on December 22, 1936. Thaddeus graduated from the Cleveland Institute of Electronics and worked as a technical specialist at the Columbus Steel Drum Company. He was married and had three children.

Gary graduated from high school in 1958. After graduation, he enlisted in the army and was assigned to the Air Force. He served in Vietnam during the early years of the war. After four years of military service, he resigned in 1962. Gary then moved back to his mother's home in Ohio, where he lived until 1977. During his time at home, he faced difficulties in finding stable work and led a marginal lifestyle.

From 1962 to 1977, Gary got into trouble with the law multiple times. He was charged with petty theft, obscene behavior in public places, and illegal possession of weapons. In 1977, Thaddeus divorced his wife. He fell into a serious emotional state after the divorce. Around the same time, Gary was experiencing financial struggles. This led to Gary persuading Thaddeus to commit a series of robberies together.

The Lewingdon brothers, Gary and Thaddeus, committed a series of murders in Ohio between 1977 and 1978. They targeted strangers away from their homes. Their first known murder occurred on December 10, 1977, when they shot and robbed Joyce Vermillion and Karen Dodrill in a bar in Newark. Dodrill died on her 34th birthday.

On February 13, 1978, they broke into the home of Robert McCann, a nightclub owner, along with his mother Dorothy and his girlfriend Christine Hardman. They shot all three victims in the head during the robbery. Then, on April 8, they attacked Jenkins Jones, a 77-year-old man, and shot him and his four dogs before stealing from his house. The Lewingdons killed a priest named Gerald Fields on April 30 in Fairfield County.

Later, on May 22, they murdered Jerry Martin and his wife Martha in their home in northeast Columbus. They shot both victims through the window and stole their valuables. Forensic analysis later revealed that the same gun was used in several of the murders.

By the fall of 1978, Thaddeus decided to stop working with Gary. However, Gary, facing financial problems, killed Joseph Ennik on December 4. Shortly after, on December 8, Gary was caught trying to use Ennik's stolen credit card and was arrested. Thaddeus was arrested a few days later based on Gary's confession.

Both brothers faced multiple murder charges. In January 1979, they changed their pleas to not guilty. However, evidence found in their homes linked them to the murders. In February, Thaddeus confessed to several of the killings. He received a life sentence, and later received additional sentences for other murders. Gary was also found guilty of multiple killings and sentenced to life imprisonment.

After their convictions, Gary began to show signs of mental distress and attempted to escape from prison. He was later moved to Lima State Hospital. Gary died on October 24, 2004, due to heart disease, while Thaddeus passed away from lung cancer on April 16, 1989.