John William Hopkins was born on June 3, 1953, in Johnstown, New York. He had two brothers named Jimmy and Donny, and a sister named Nancy. Information about his childhood is limited. However, during his teenage years, he showed interest in becoming a state police officer but later decided against it.

Hopkins enjoyed spending time on the New York State Thruway. He often cruised in his Chevy Nova and visited college towns. He would frequently wear a cowboy hat and a military coat. Some friends and acquaintances noted that he wanted to look like a police trooper. Additionally, Hopkins had a strong fascination with knives. He often carried multiple knives with him, kept in different sheaths.

On January 12, 1972, John William Hopkins abducted 19-year-old Joanne Pecheone. She was walking along a wooded path in East Utica. Hopkins bound and gagged her, then committed assault before ultimately stabbing her multiple times. While leaving the scene, he was startled by a boy on a snowmobile, prompting him to flee into the woods. This boy later discovered Pecheone's body and contacted law enforcement. Lt. Raymond Pecheone, one of the first responders, had to step down from the case upon realizing Joanne was his niece. Despite eyewitness accounts, Hopkins was not identified as a suspect, and Pecheone's murder became a cold case.

On the night of July 24-25, 1976, Hopkins kidnapped 17-year-old Cecelia Genatiempo from a donut shop in Gloversville. He took her to a remote railroad track in Mohawk, where he raped and stabbed her multiple times before hiding her body in a shallow grave. Her decomposed body was found three months later by hunters in the area.

Hopkins' final confirmed victim was 17-year-old Sherrie Ann Carville. On October 22, 1978, he abducted her from a bar in Johnstown and drove her to his father's property. There, he raped and stabbed her several times before leaving her body in a field. A year later, another man, Albert J. Baird, was initially arrested for her murder after confessing, but he was cleared of suspicion.

On August 15, 1979, Hopkins kidnapped a 15-year-old girl from Northville. He took her to his home in Johnstown, where he restrained her and sexually assaulted her. The next day, he intended to kill her, but he was interrupted by a logger working nearby. The girl and the logger reported the incident to the police, leading to his arrest. After a few hours of questioning, Hopkins confessed to several crimes, including the murders of Genatiempo and Carville, but he did not mention Pecheone.

Hopkins faced multiple trials for his crimes. He was convicted of two murders and the attempted murder of the Northville girl. He received a 25-year-to-life sentence for each, to be served consecutively. After a short time in prison, he was tried again for Carville's murder and received another 25-year-to-life sentence. He faced one final trial for the attempted murder, with a similar outcome. His appeals were rejected by the court.

Hopkins remained in prison until March 11, 2000, when he took his own life using a razor. In 2011, the Oneida County District Attorney publicly named him as the killer of Joanne Pecheone, although DNA evidence was inconclusive. There has also been speculation about other potential victims, but no definitive links have been established.