Gary Michael Heidnik was born on November 22, 1943, in Eastlake, Ohio. He had a younger brother named Terry. When Gary was a child, his parents divorced, and he lived with his mother for a while before moving in with his father and stepmother. Gary's relationship with his father was difficult. He claimed that his father was emotionally abusive and would humiliate him when he wet the bed by hanging the stained sheets out for everyone to see.

At school, Gary was a loner and did not make friends easily. He performed well academically and had a high IQ of 148. Encouraged by his father, he attended Staunton Military Academy for a time but did not graduate. Eventually, he dropped out of high school and joined the U.S. Army at the age of 17. During his service, he was trained as a medic and served in Germany. However, he began experiencing severe headaches and was diagnosed with a mental disorder, leading to his honorable discharge in 1962.

After leaving the Army, Gary became a licensed practical nurse and enrolled at the University of Pennsylvania, but he dropped out after one semester. He worked at a Veterans Administration hospital but was fired for poor attendance and rude behavior. Over the years, he was in and out of psychiatric hospitals and attempted suicide multiple times. In 1970, his mother committed suicide, and his brother also struggled with mental health issues.

In 1971, Gary started a church called the "United Church of the Ministers of God" and managed to build a significant amount of wealth through it. He used a matrimonial service to meet his future wife, Betty Disto, and they married in 1985. The marriage quickly fell apart due to Gary's abusive behavior, and Betty left him after a few months. During his life, Gary fathered several children, some of whom were placed in foster care due to his unstable and abusive nature.

Gary Heidnik, a disturbed individual, committed his horrific crimes between November 1986 and March 1987. He kidnapped, tortured, and raped six women, holding them captive in a pit he dug in the basement of his Philadelphia home. His victims were often lured with promises of money or help, only to find themselves trapped in a nightmare.

Heidnik's first victim was Josefina Rivera, whom he kidnapped on November 25, 1986. Over the next few months, he abducted Sandra Lindsay, Lisa Thomas, Deborah Dudley, Jacqueline Askins, and Agnes Adams. The women endured unimaginable horrors, including starvation, beatings, and torture. Heidnik would often electrocute them by filling the pit with water and using a live wire.

Sandra Lindsay, one of the captives, died from a combination of starvation, torture, and an untreated fever. Heidnik dismembered her body, cooking parts of it and allegedly mixing her flesh with dog food to feed the other captives. Another victim, Deborah Dudley, was killed by electrocution when Heidnik forced Josefina Rivera to help apply electric shocks to her chains.

On March 23, 1987, Heidnik kidnapped Agnes Adams. The next day, Rivera convinced him to let her visit her family temporarily. Instead, she contacted the police, leading to Heidnik's arrest. The police raided his house, freeing the remaining captives and ending their torment.

Heidnik was charged with multiple counts of kidnapping, rape, and murder. His trial revealed the extent of his brutality, and he was sentenced to death. On July 6, 1999, Gary Heidnik was executed by lethal injection, making him the last person to be executed in Pennsylvania as of that date.