A man walked into an Oregon FBI field office and voluntarily confessed to murdering and raping a woman more than four decades ago in Massachusetts, prosecutors announced Monday.

John Michael Irmer, 68, was transported from Portland, Oregon, to Boston over the weekend and was arraigned on Monday. Irmer faces charges of first-degree murder and aggravated rape.

"Nearly 44 years after losing her at such a young age, the family and friends of Susan Marcia Rose will finally have some answers," Suffolk County District Attorney Kevin Hayden said in a statement.

Last month, Irmer told FBI agents that he had met a woman with red hair around Halloween in Boston in 1979, according to prosecutors. Irmer said he killed the woman and then raped her before fleeing to New York the next day.

After taking a DNA sample from Irmer, investigators said it was a match with DNA samples preserved from the crime scene.

Irmer was ordered to be held without bail on Monday and is pending another court appearance on Oct. 17. Steven Sack, the attorney representing Irmer, said he wouldn’t contest bail but noted Irmer’s decision to voluntarily turn himself in.

"I would say on his behalf, he was a free man for 10 years. He walked into police and confessed, allegedly," Sack said.

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Victim identified as 24-year-old woman

Irmer allegedly told FBI agents that he had met the woman at a skating rink. Irmer said the two had walked into an apartment building in Boston's Back Bay neighborhood that was under renovation, according to prosecutors.

Shortly after, Irmer said he grabbed a nearby hammer and bludgeoned the woman on the head. Prosecutors said he then raped the woman.

Investigators confirmed that the victim was Susan Marcia Rose, a 24-year-old woman who was found dead at the Back Bay apartment building on October 30, 1979. Rose had moved from Pennsylvania to Boston and lived just south of the crime scene.

Rose's cause of death had been determined to be multiple blunt injuries of the head with fractures of the skull and lacerations of the brain, according to authorities. Prosecutors said another man had been arrested at the time of her murder but was found not guilty in June 1981. 

"This was a brutal, ice-blooded murder made worse by the fact that a person was charged and tried—and fortunately, found not guilty—while the real murderer remained silent until now," Hayden said in the statement. "No matter how cold cases get resolved, it’s always the answers that are important for those who have lived with grief and loss and so many agonizing questions."

Confessed to another crime

Prosecutors say that Irmer is being further investigated after he confessed to another slaying.

Prior to his confession of the 1979 murder, investigators said Irmer had been free for 10 years. He had previously served three decades in prison for a homicide in California.

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Contributing: The Associated Press