Troy Leon Gregg was born on April 29, 1948, in Asheville, North Carolina. Details about his early life are sparse, but by his mid-20s, he was known to be transient, often hitchhiking across states. On November 21, 1973, while hitchhiking with 16-year-old Floyd Allen, they were picked up by Fred Simmons and Bob Moore in Florida. The group later picked up another hitchhiker, Dennis Weaver, who left the group in Atlanta. That night, Simmons and Moore were murdered in Georgia. Gregg was arrested three days later in Asheville, North Carolina, found in possession of the murder weapon.

On November 21, 1973, Troy Leon Gregg and Floyd Allen were hitchhiking when they were picked up by Fred Simmons and Bob Moore. After traveling together, the group stopped in Gwinnett County, Georgia. According to Allen's testimony, Gregg decided to rob Simmons and Moore, shooting them as they returned to the car. He then approached the wounded men and shot each in the head at close range, stealing their money and belongings. Gregg and Allen fled in the victims' car.

Gregg was arrested on November 24, 1973, in Asheville, North Carolina. He was tried and convicted of two counts of murder and armed robbery on November 24, 1974. His case, Gregg v. Georgia, became a landmark Supreme Court decision in 1976, reinstating the death penalty in the United States under revised statutes.

On July 28, 1980, the night before his scheduled execution, Gregg escaped from Georgia State Prison along with three other inmates by disguising themselves as correctional officers. They sawed through cell bars and a window, then used a car left by an accomplice to flee. Gregg was found dead the next day, July 29, 1980, in North Carolina, having been beaten to death. The exact circumstances of his death remain unclear, with theories ranging from a bar fight to a dispute with fellow escapees.