A north Texas woman told investigators she had planned for at least two weeks to kill her young daughters and husband before she fatally shot the girls early Thursday morning.

Sarah Nicole Henderson, 29, was arrested after her husband, Jacob Henderson, called 911 to report the shootings at their home near Mabank, a town about 55 miles (89 kilometers) southeast of Dallas. The girls were ages 5 and 7.

The woman was charged with one count of capital murder, but Henderson County Sheriff Botie Hillhouse said another capital murder charge is pending and other charges are possible. Her bond was set Friday at $2 million, and she was being held at the Henderson County Jail on suicide watch, Hillhouse said.

Hillhouse said Henderson confessed when talking to investigators and said she had been planning to kill the girls and her husband for several weeks. She also told investigators she planned to kill herself, he said.

"She did try to shoot her husband. The gun malfunctioned. He took the pistol then realized the daughters had been shot," Hillhouse said. "We don't have a motive at all. We're still digging, trying to figure out what was going on at that house at the time."

Jacob Henderson had initially called 911 about 11:30 p.m. Wednesday to ask for medical help for his wife. According to a recording of that call provided by the sheriff's office, he tells operators that she won't listen to him and that she is, "freaking out like someone is out to get her."

He calls back to cancel the call a few minutes later saying that Sarah told him she's fine now and is acting normally. The call was coded as a potential suicide when reported to the sheriff's office. Deputies responded to the house about 11:45 p.m., when the couple told deputies they were OK and didn't need help.

Jacob Henderson called 911 again about 2:24 a.m. to report that his wife had shot the girls. He can be heard sobbing and asking why she had done it in the recording released by the sheriff's office.

"She was asleep when I went to sleep last night. I woke up and she came in there said, 'Babe, I just shot the kids.' And I didn't want to believe it. I went in there and they were dead," Jacob Henderson tells the 911 dispatcher.

He said the girls were asleep in the living room, and that they had both been shot in the head.

Sarah Henderson can be heard in the background asking her husband to kill her or shoot her, saying people are after her and that they're coming. At one point in the recording she yells, "God, what did I do?"

Hillhouse said Jacob Henderson is not the biological father of the girls, and their father has been notified. He said Sarah Henderson has an older son who lives with his father and was not in the house at the time of the shooting.

Deputies had been called to the house twice before for minor complaints, Hillhouse said. In 2015, a neighbor reported a verbal altercation that ended up being Sarah Henderson having an argument with someone on the phone outside the house. The couple also reported a suspicious vehicle in their area a few months later.