WILLMAR — A Willmar teen pleaded guilty Wednesday in a plot to burglarize and kill his grandmother last summer and was sentenced to life in prison with the possibility of parole after 30 years.

Robert Warwick, 18, pleaded guilty in a packed room in the Kandiyohi County Courthouse to first-degree murder while committing a felony. Another count — of first-degree premeditated murder — was dismissed.

Warwick was scheduled for trial next month. The plea deal averted a trial that would have been painful for Warwick’s family, defense attorney Daniel Mohs said last week.

Prosecutors say Warwick hatched the plan to rob and murder his grandmother, 79-year-old church volunteer Lila Warwick, in her Willmar home.

Robert Warwick apologized to his relatives, several of whom wept in the courtroom.

“I hope one day everyone will forgive me,” he said. “I want to say sorry to my grandma, who’s watching over me every day of my life.”

Cheri Ekbom, Lila’s daughter and Robert Warwick’s aunt, took the witness stand to read the third victim impact statement she had fashioned for the prosecution of the three teens charged in this case.

“Unlike the others, I do not look into the eyes of a stranger, but that of family. My nephew, Robbie Warwick. There are still unanswered questions,” she said.

“Really, just one: Why?” Ekbom said, turning to look at Robert Warwick.

The plea agreement concludes the prosecution of three teens for the crime that left Lila Warwick handcuffed and bleeding on her basement floor.

Robert Warwick’s friend, Brok Junkermeier, now 20, pleaded guilty in the middle of his trial in April to killing the woman and was sentenced to life in prison without parole.

Junkermeier testified that he and Warwick, who was 17 at the time, had been planning the July ambush robbery and attack for months. In the hours after Lila Warwick’s slaying, the pair returned to her home and stole her safe, which they expected to contain tens of thousands of dollars, Junkermeier told investigators.

A third teen pleaded guilty in December for acting as a lookout.