West Jordan • A former Utah high school health teacher pleaded guilty Friday to aggravated murder and other charges, admitting she shot and killed her ex-husband’s girlfriend.

Chelsea Watrous Cook, 33, went to her ex’s apartment on Nov. 25, 2019, and fatally shot 26-year-old Lisa Vilate Williams in front of Cook’s 3-year-old twins.

Cook pleaded guilty to aggravated murder, aggravated burglary, three firearm-related felonies and two misdemeanor charges of committing a violent offense in front of children.

She showed little emotion through Friday’s hearing, calmly saying, “guilty” to each charge as the judge asked for her plea. She began to cry as she admitted to the charges involving violence in front of her children.

The woman is expected to be sentenced on May 18. Aggravated murder carries a penalty of 25-years-to-life in prison, and she has agreed to have the remaining penalties run back-to-back to that sentence. How much time she actually serves behind bars, however, will be up to the parole board.

Prosecutors allege that Cook had initially gone to her ex-husband’s apartment that November evening to give her children cold medicine.

They had texted each other and arranged to meet outside the apartment, but when the man went outside, Cook instead went inside, prosecutors wrote. The man returned to find Cook in the living room with Williams and the two children, prosecutors wrote.

After Cook refused to leave, her ex picked up the phone to call 911, and Cook briefly locked herself in a bathroom, prosecutors wrote. She came out of the bathroom and walked toward her coat, prosecutors wrote. Her ex-husband then heard multiple gunshots and saw Cook pointing a gun at Williams, who was fatally shot in the chest, as well as in the leg and hip, prosecutors wrote.

The man grabbed the gun from Cook, who then sat with the children, prosecutors wrote. Cook’s ex-husband tried to call 911 again, but Cook got up and again walked to her coat; the man, worried she had another gun in the coat, pinned her to the wall until police arrived and told the children to go into their room and lock the door, prosecutors wrote.

Cook taught health at Skyridge High School in Lehi.