WILLMAR — A 16-year-old has pleaded guilty to unintentional second-degree murder for his role in the killing of a 79-year-old Willmar grandmother.

Lila Warwick was slain during a robbery at her home July 29.

Under Tuesday’s plea agreement, the 16-year-old lookout will get an extended juvenile sentence that will run until he turns 21, and a stayed 15-year adult sentence in case he violates the conditions of his juvenile sentence. Sentencing is set for Jan. 27.

Nineteen-year-old Brok Junkermeier and 18-year-old Robert Warwick, both of Willmar, have been indicted on first-degree murder charges in the case. Warwick allegedly masterminded the crime, suspecting his grandmother had more than $40,000 in a safe. Junkermeier allegedly stabbed and strangled her after making her write him a check.

Both face prison sentences of life without parole.