OKMULGEE, Okla. (AP) — An Oklahoma woman accused of killing her 18-year-old son and wounding a teenage daughter told investigators she shot her children in their heads while they were sleeping, according to an affidavit released by police Friday.

The affidavit said Amy Hall, 38, told the Okmulgee County Sheriff’s Office on Thursday that she shot her son, Kayson Toliver, while he slept in his bed early that morning. He was found dead at when deputies arrived at a home in the Nuyaka area, about 35 miles (55 kilometers) southwest of Tulsa.

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Hall also said in the affidavit that she shot her 16-year-old daughter in the head while she slept. The girl remained in serious condition Friday.

The mother said she tried to shoot her 14-year-old daughter, according to the affidavit, but she escaped into a bathroom and began to cry. The girl told her mother “it was OK,” then left the bathroom and was able to take a pistol from Hall.

The sheriff’s office said they do not release names of surviving juvenile victims.

Hall told police that she had intended to kill herself after killing her children but her plan was interrupted when her younger daughter took the gun.

After shooting her children, Hall left the scene, said sheriff’s office spokesman Duston Todd. She drove for several miles at over 100 mph before finally stopping.

A fourth person, an 18-year-old man who was sharing a bed with Tolliver, was not harmed. Hall said in the affidavit she had not planned on shooting him.

Authorities are still investigating a motive, but Hall said in the affidavit “some part” of her was trying to protect her children from who she claimed was an abusive father.

Hall and the children’s father were separated and were engaged in a two-year custody battle. Last month, Hall filed an emergency order asking for temporary sole custody of the children. In 2016, the man claimed that Hall was mentally unstable and was psychologically abusive to the children.

Hall has been preliminarily charged with one count of first-degree murder and two counts of shooting with intent to kill. Bond has been set for $500,000 each for the shooting charges. No bond has been set for the murder charge.