MINNEAPOLIS -- A 19-year-old man on trial for killing his friend's grandmother has pleaded guilty, according to the Kandiyohi County Court.

Brok Junkermeier is accused of choking and stabbing 79-year-old Lila Warwick inside her home last summer.

Warwick's grandson, Robert (Robbie) Warwick, 18, is charged with masterminding the murder. He will face first degree murder charges later. Authorities say that Junkermeier and Warwick planned to rob the woman.

A third teen has already been sentenced for acting as a lookout.

Junkermeier is set to be sentenced next Wednesday.