A double murder that had gone unsolved for nearly 16 years came to a close with a guilty plea Monday.

Jason Preston, 37, admitted in court that on Christmas Eve 1998 he was responsible for the deaths of 18-year-old Carrie Richter and 20-year-old Dustin Baity. Preston wasn’t charged in the Minneapolis slayings until 2014, when DNA found at the scene matched his. He pleaded guilty to two counts of second-degree murder.

Preston, who had been serving a prison sentence in California when he was charged, said in court that he was at Baity’s apartment when an argument ensued over a drug debt. The fight escalated and he strangled Baity with a cord. He said he held Richter as someone else stabbed her.

A spokesman for the Hennepin County attorney’s office, Chuck Laszewski, said that Preston told authorities just Monday morning that another person helped him kill Richter. Preston would not identify that suspect. No DNA was found at the home that would match anyone other than Preston and the victims, Laszewski said.

“Based on DNA results and the fact that he never mentioned an accomplice until today, we are quite certain we have the only killer of this young couple who were starting out their lives together,” Hennepin County Attorney Mike Freeman said in a statement.

Preston will be sentenced in January to 48 years in prison.

His lawyer, Jim Kamin, said that sentence cannot be reduced, even if Preston gives information on the other person he said helped kill Richter.

During the hearing, Preston told the families of Richter and Baity he was “truly sorry.”

“I just pray that they have some closure today,” he said.