Authorities say they were able to solve a Boston cold case from 44 years ago after an Oregon man walked into an FBI office and confessed to killing a raping a woman in 1979.

John Michael Irmer, 68, was arraigned in a Boston courtroom Monday and charged with murdering 24-year-old Susan Marcia Rose on October 30, 1979, according to a news release from the Suffolk County District Attorney's Office.

In August, Irmer walked into a Portland FBI field office where he revealed to agents he met a woman with red hair at a Boston skating rink around the time of Halloween in 1979 and killed her, the DA's office said.

Irmer said they walked into 285 Beacon Street, a building under renovation at the time, grabbed a hammer and hit the woman on the head, killing her. He told FBI agents he raped her after she had died, the news release said.

After the admission, authorities were able to confirm Rose, who had red hair, was found murdered on Beacon Street, a historic thoroughfare near the heart of the city, the DA's office said. Her cause of death was ruled to be multiple blunt injuries to the head with fractures of the skull and lacerations of the brain.

The DA's office said investigators were able to match a DNA sample from Irmer with samples collected from the murder scene.

Another man was tried and found not guilty of Rose's murder in 1981, the press release stated. No information was immediately available about the prior case.

During Monday's arraignment, Assistant District Attorney John Verner said that while Irmer was confessing to Rose's murder, he also admitted to committing another murder in a southern state. Verner said authorities were looking into the admission.

Additionally, Verner said Irmer told police he had served "about 30 years" in prison for another killing in California.

Attorney Steven J. Sack, who represented Irmer in court Monday, said he doesn't contest bail. He said Irmer came to court "without a fight to face these charges."

Irmer is in custody and is currently being held without bail.

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

The Suffolk County's Attorney Office told CNN they are not commenting on Irmer's case at this time.