In a surprise move, the 19-year-old on trial in Willmar, Minn., for allegedly killing Lila Warwick, his friend's grandmother, has pleaded guilty to one charge of first-degree, premeditated murder.

The fourth day of testimony in the trial of Brok Junkermeier was set to resume at 1:15 p.m. Wednesday, but attorneys were meeting behind closed doors. When they emerged, Junkermeier went into the chambers of Judge Donald Spilseth.

Junkermeier said that he was changing his plea because he committed the crime and to keep "the families from having to listen to more of the evidence."

"You don’t want anybody to have to hear anymore," his attorney Kent Marshall said.

"No, I don’t," Junkermeier said.

Marshall and Spilseth questioned Junkermeier on the stand, asking whether he understood that the penalty for first-degree, premeditated murder is life in prison without the possibility of parole. Junkermeier said yes.

Junkermeier had faced two charges -- first-degree, premeditated murder and first-degree murder in the course of a burglary. In a four-hour, videotaped interview with investigators, he admitted to carrying out the July ambush robbery and attack prosecutors say he planned with Warwick’s grandson, Robert Inocencio Warwick, 18.

Sentencing will be held next week. Lila Warwick's daughter, who declined to comment Wednesday afternoon, will make a statement then.