A Massachusetts teenger will spend 28 years behind bars for his part in the murder of his friend's Mom, last year in Maine.

17-year-old William Smith pleaded guilty on Monday, as part of a plea deal with prosecutors. He's accused of killing Kimberly Mironovas, in  April of 2018. Police said the victim's son, Lukas, and two of his friends got angry when she refused to drive them back to Massachusetts, so prosecutors say Smith came up with a plan to kill her. The boys choked her and, when she lost consciousness, Lukas stabbed her several times in the throat.

All three teens pleaded guilty to murder. WABI-TV reports Smith was tried as an adult and will spend 28 years in prison. Lukas Miranovas is due to be sentenced in December, while a third teen, who was 13 at the time of the murder, will remain in juvenile detention until he's 21.