For at least a month, police say, Nicole Lester had been searching on her cellphone for ways to kill someone.

“How do you break a neck?” she typed into Google. And, she later asked: “Where is the best place to hit a person with an ax?”

Officers allege that they found the questions when reviewing Lester’s browser history. Toward the end of the list, they report, the searches started to be specifically about children. Looking up a medical diagram of a child’s chest and ribs. Studying cases in other states where kids were murdered. Asking if it was easier to kill a toddler than an adult.

Then — on Dec. 31 — one day after her last query, police say Lester stabbed to death her 4-year-old daughter.

Based on that preliminary evidence and accounts from officers, prosecutors filed charges Wednesday against Lester. She faces one felony count for aggravated murder — which means she could face the death penalty.

Police were first called to Lester’s house near 4500 W. Losee Drive in West Valley City on New Year’s Eve at 5:02 a.m. Lester had walked to the house next door and apparently told a neighbor that she had killed her daughter. The neighbor dialed 911.

At one point, according to court documents filed Wednesday, the dispatcher said she could hear Lester shout, “I just killed my daughter.”

When officers arrived, they say, the 29-year-old woman repeated, “I need to be arrested now.”

Police entered the home and found a child’s body in the basement. The graphic and detailed probable cause statement says the 4-year-old had been stabbed at least 30 times. A medical examiner reported that the girl’s shoulder and wrist were partially severed, a result of her trying to fight back. The girl also had deep cuts to her chest “centered on her heart,” the documents state, but some wounds also pierced her lungs and spine.

Officers reported finding a sharp ceramic kitchen knife nearby.

A 6-year-old boy was discovered sleeping in a main floor bedroom; he was unharmed. The house is owned by Lester’s mother, who was not home at the time. She later returned and took custody of the boy.

Officers have reviewed the scene and Lester’s phone history during their investigation. That’s when they discovered what she had been searching for prior to the attack.

Lester is being held at Salt Lake County jail.

She has previously pleaded guilty to assault in May 2014 in a case involving domestic violence. The charge was dismissed after Lester completed court-ordered mental health treatment.