Harvey Carignan, a serial killer and rapist who murdered three women in Minnesota and Alaska nearly 50 years ago, died this month at Oak Park Heights prison.

He was also suspected in more killings, and was convicted in the 1970s in at least five sexual assault and rape cases against women and children as young as 13.

Carignan was 95 and died of natural causes March 6, the Minnesota Department of Corrections confirmed Wednesday. After imprisonment, Carignan became known as the "Want-Ad Killer," which was the title of the 1983 true-crime book that Ann Rule wrote about him.

The title referred to Carignan's practice of luring young women through job postings in classified ads.

Carignan grew up in North Dakota, and his first murder case came at age 22 in 1949, when he was stationed as an army soldier in Alaska. He beat and killed 57-year-old Laura Showalter in Anchorage, and her body was later found in an empty lot.

Carignan was convicted of murder and sentenced to be hanged. But he was released when an appeals court ruled the conviction was invalid because there was no testimony that his confession was obtained voluntarily, the Minneapolis Star reported at the time.

He was convicted for assaulting a different woman in Alaska and incarcerated for a little over 10 years before getting released on parole from Alcatraz Penitentiary in 1960.

In 1972 and 1973, police in Washington state identified Carignan as the suspect in the murders of 15-year-old Kathy Miller and 19-year-old hitchhiker Leslie Laura Brock, but never brought charges because of a lack of physical evidence in those cases.

The first Minnesota murder was in 1974, that of his ex-girlfriend Eileen Hunley, 29, whom Carignan lived with after moving to Minneapolis. Hunley, who worked at a day care, was beaten to death in August 1974. Authorities found her body in a field near Zimmerman.

During a trial in the case of a Minnesota girl who survived after Carignan kidnapped and assaulted her, Carignan testified he was sorry he did not succeed in killing her, because "God told him to humiliate and kill her," and he would "try to fulfill that command now if he had the chance," the Star reported.

In September that year, Carignan was also charged with the murder of 18-year-old Katherine Schultz, who was found dead in a cornfield northwest of Cambridge, Minn.

During trials, Carignan's attorneys argued he should be found not guilty because of mental illness, which meant arguing that he could not understand the nature of the acts or determine right from wrong.

A juror told the local newspaper that the panel felt the man was mentally ill to a degree but that they believe Carignan also knew what he was doing and was capable of judging his own actions.

Douglas Thomas, one of Carignan's attorneys, referred to his client during court as a "shell of a human being," a "homicidal maniac" and a "stainless steel schizophrenic."