One of two people charged in the 1988 beating death of a pregnant mother in northwestern Indiana has pleaded guilty to murder.

George Kearney, 78, entered the plea Monday, about three years after he agreed to speak with police about the killing of 28-year-old Miriam Rice, St. Joseph County prosecutors said.

Rice, of South Bend, was abducted June 24, 1988, while walking her dog in a park. Her body was found about a week later obscured by foliage down an embankment.

Kearney's former girlfriend, Barbara Brewster, 56, also was charged with murder last year and is due to stand trial. Brewster has told investigators that Kearney killed Rice. She faces a hearing Tuesday.

Kearney, Brewster and Brewster's three young children were camping and fishing in the park when Rice was killed.

Brewster's now-adult son, Robert South, told investigators that he saw Kearney drag Rice into their van and his mother beat her in the head with tools that were in the vehicle, according to court documents filed last July by prosecutors.

His older sister, Paula Brooks, now in her 30s, told investigators that Kearney, Brewster and South left the campsite to get food.

"A couple of hours later she heard a 'blood-curdling scream' from across the lagoon from a woman," St. Joseph County Metro Homicide Unit cold case investigator Brett Coppins wrote in an affidavit. "This unknown woman was pleading for her life. The screaming continued for some time."

When they returned, all three were covered with blood, Brooks said.

"Robert stated that he has been traumatized by this murder his whole life," Coppins wrote. "He stated that he has never told anyone what happened because George Kearney threatened to kill him if he did."

Kearney was arrested in July 1988 in an unrelated case and spent 27 years in prison. After his release, he reached out to investigators in 2016 and said Rice was killed by Brewster, according to the affidavit.

"He stated that he had been getting letters while in prison from Paula (Brewster's daughter) questioning his involvement in the death of Miriam Rice," Coppins wrote. "In order to 'clear the air,' George Kearney advised officers that he wanted to come forward."

Brooks also told police she wrote to Kearney in an attempt to get him to admit to "what he had done to Miriam Rice."

At the time of her death, Rice was married, four months pregnant and had a 3½-year-old child.

No motive or discussion of motive behind the slaying was included in an affidavit in the original charging documents, a spokeswoman for the prosecutor's office told The Associated Press Monday in an email.

Kearney faces 40 to 60 years in prison when sentenced March 29.