Douglas Edward Gretzler was born on May 21, 1951, in the Bronx, New York. He was the second of four children in the family. His parents were Norton Tillotson Gretzler and Janet Greta Bassett. Norton was an important figure as he served as President of the Tuckahoe School District, while Janet was a homemaker. In the early 1950s, the family moved to Tuckahoe, a working-class suburb known for its decent residents.

Growing up, Douglas had a troubled childhood. His father was strict, expecting high obedience and academic success from his children. He often used physical and mental punishment when they fell short. Douglas often felt overshadowed by his older brother Mark, who was favored by their father for his academic achievements and popularity. In contrast, Douglas struggled in school, earning mostly C and D grades, and was not particularly successful as a Boy Scout.

By age eleven, Douglas stopped trying to please his father, opting instead to pursue activities outside of home like playing the drums in the basement. In 1966, he began experimenting with marijuana, which created more tension between him and his father. Their arguments got heated, especially when his father discovered his drug use. Despite attempts by his parents to repair their relationship through family counseling, the efforts were mostly unsuccessful.

Tragedy struck the family on August 16, 1966, when Mark, at the age of 17, committed suicide. This added more strain to the family dynamics, and Douglas's father expressed his sorrow in a drunken state, questioning why Mark was the one to die.

During his teenage years, Douglas began to experiment with harder drugs like mescaline and LSD, which worsened his relationship with his father. He attended Tuckahoe High School and earned the nickname "Lamby." Although he played on various sports teams, he was only average at best. Music remained his main passion, especially playing the drums.

After graduating in 1969, instead of pursuing further education, Douglas started working as an auto mechanic. A year later, he moved to Florida, where he met Judith Eyl, and they began dating. They soon got married in February 1970 and moved back to the Bronx. Despite holding several jobs, Douglas often quit after short periods, which led to conflicts with Judith, who worked full-time at a bank. They had a daughter named Jessica in 1972, but Douglas started spending more time away from home.

Despite receiving a significant trust fund on his 21st birthday, most of the money went toward buying a sports car rather than supporting his family. Later that year, feeling increasingly burdened by family responsibility and financial struggles, Douglas abruptly left Judith and their baby to head west in his car, with the aim of moving to Colorado. He ended up in Casper, Wyoming, where he lived for about six months, taking on low-paying jobs until he was arrested for a minor traffic violation.

In October 1973, Douglas Edward Gretzler and his accomplice Willie Steelman began a series of violent crimes in Arizona and California. Their first major acts were the kidnapping and murder of two young men, Kenneth Unrein and Michael Adshade, on October 18, 1973. They were taken at gunpoint and later killed near Littlejohn Creek in Knights Ferry, California.

Following their initial murders, Gretzler and Steelman continued their crime spree. They kidnapped a couple, James Fulkerson and Eileen Hallock, on October 20, 1973. Steelman attempted to rape Hallock but was unable to do so. Instead, they robbed the couple and released them afterward.

On October 23, they murdered an 18-year-old hitchhiker named Steven Loughran. After torturing him, they shot him in a gully near the Superstition Mountains. Shortly after, they killed Robert Robbins on October 24, 1973, while his girlfriend, Katherine Mestites, was at work. They strangled him and shot him to ensure he was dead. Mestites was murdered the next day.

In the days that followed, they abducted and murdered a young couple, Michael and Patricia Sandberg, on November 3, 1973. After taking their lives, they returned to Tucson and continued their violent actions.

The most notorious of their crimes occurred during the Parkin-Earl-Lang massacre on November 7, 1973. They invaded the home of the Parkin family, taking ten people hostage, including two small children. Despite initially intending to rob the family, they executed all seven adult and teenage hostages, including the Parkin children, in a brutal act of violence.

Gretzler and Steelman's rampage ended when they were apprehended on November 8, 1973. Both were later tried and convicted for their numerous murders, leading to sentences of life imprisonment and death. Gretzler was executed by lethal injection on June 3, 1998.