William Dean Christensen was born on September 24, 1945, in Bethesda, Maryland. Details about his early life are not widely known. He grew up in a time when many social changes were happening in the United States. Little is documented about his family or childhood experiences.

In 1969, when Christensen was 24 years old, he began to get into trouble with the law. He picked up a 19-year-old hitchhiker in Georgetown, Washington D.C. He took her to a remote area where he attacked her. The young woman survived, and Christensen was arrested. He was sentenced to five years in prison for this crime, but instead of serving time in prison, he was sent to a state facility for delinquents. He was released after one year, in 1970.

In 1974, Christensen was involved in another serious crime. He and an accomplice kidnapped a go-go dancer in Georgetown. They took her to a secluded spot where they assaulted her. Eventually, they drove her to Christensen's parents' house, where the attack continued. Both men were arrested, and Christensen received a sentence of 16 years in prison. He was released early, in 1980.

After his release, Christensen committed another crime in July 1980. He abducted a young woman at a bus stop in Washington D.C. He took her to a relative's home where he assaulted her. Following this crime, arrest warrants were issued for him. In January 1981, while attempting to move to Toronto, he was arrested for providing false information on his passport. He spent 21 days in jail before being released.

After his release, Christensen created a false identity named Richard Owen. In April 1981, using this name, he kidnapped and assaulted a woman in Montreal. He pleaded guilty to this crime and was sentenced to a year and six months in prison. It was later discovered that Richard Owen was actually Christensen, who was wanted for his past crimes in Washington D.C. The authorities tried to transfer him back to Maryland, but a clerical error resulted in his accidental release.

In April 1982, William Dean Christensen committed his first known murders in Montreal. He abducted 27-year-old Sylvie Trudel and brought her to an empty apartment. There, he raped, beat, and strangled her to death. He then decapitated and dismembered her body using a hacksaw. Later that same month, Christensen killed 26-year-old Murielle Guay in a similar manner and dismembered her body as well. On April 27, 1982, both victims' remains were found. Sylvie Trudel had been dead for about 20 to 30 hours, while Murielle Guay had been dead for 10 days.

Christensen was quickly identified as a suspect because he owned the apartment where Trudel's body was found. Witnesses also reported seeing him with Guay. Facing arrest, he fled to the United States. Canadian authorities issued warrants for his capture and interviewed Christensen's parents, who admitted to meeting him and giving him money while he was on the run.

Throughout the months, Christensen was reported in several U.S. states, including Florida, New York, New Jersey, Georgia, Kentucky, and Pennsylvania. During this time, he used the alias "John Robert Schrader." On September 23, 1982, he picked up a 23-year-old go-go dancer named Michelle Angiers in Scranton, Pennsylvania. He drove her to Dickson City, where he raped and stabbed her 30 times, resulting in her death.

On June 29, 1983, Christensen shot two men at an Amtrak railroad station in Trenton, but both men survived the attack. He went on to create another alias, "Jeffrey Shrader." On December 4, 1983, after an argument, he shot and killed 51-year-old Joseph Connelly outside a bar. Witnesses reported the incident, which led to Christensen's arrest later that day.

Initially, Christensen claimed to be Jeffrey Shrader and was not immediately identified. He was convicted of Connelly’s murder, but the FBI later confirmed his true identity. After being on the run for nearly two years, authorities believed he may have committed over a dozen additional murders across different regions. Investigators linked Michelle Angiers' murder to him in early 1985, following the discovery of a bloody knife and hacksaw in his residence.

In 1990, Christensen was convicted of Angiers' murder and received a 10 to 20-year sentence. He also faced prosecution in Maryland for a prior rape case and was sentenced to 40 years in prison. In the same year, a cellmate claimed Christensen confessed to killing 24 people, including victims in England, Canada, and the United States. Authorities investigated these claims, but nothing was conclusively proven.

William Dean Christensen died of natural causes in prison on October 31, 1990. His death was not reported until July 1991.