SALT LAKE CITY (AP) – A former Utah teacher has pleaded guilty to murder charges in the shooting death of her ex-husband’s girlfriend, who was killed in front of the former couple’s 3-year-old twins.

Prosecutors have said Chelsea Cook killed Lisa Williams while she and the children decorated a Christmas tree in 2018. Cook pleaded guilty Friday to aggravated murder and other charges in an agreement with prosecutors. The Williams family has said Cook harassed the 26-year-old online and in person for months before the slaying.

Cook was a high school heath teacher in Lehi before her arrest.