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FRISCO (CBSDFW.COM) – The search for a missing mother and her three children in Frisco ended in tragedy on Thursday night. The mother is dead and the children were rushed to the hospital, but investigators still do not know what went wrong in this mysterious incident.

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The family was located in McKinney, in the parking lot of a Target store near the intersection of the Sam Rayburn Tollway and Custer Road. An officer with the McKinney Police Department found 39-year-old Christine Woo dead inside of the SUV which the Frisco Police Department had been looking for since Monday.

Christine Woo

Christine Woo

Woo’s three children — a 5-year-old girl, a 3-year-old boy and a 1-year-old girl — were all also found alive inside of the vehicle and taken to Children’s Medical Center in Plano, where they are reportedly doing okay. Police said that they may have been in the SUV with Woo for several days after she died.

“They were in the vehicle. They were alive,” Sgt. Jeff Inmon with the Frisco Police Department said about the children. “I can’t speculate on their condition, however, officers on the scene said they looked fine. But, as a precaution determined, they were transported to the hospital.”

Woo children

Woo Children

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There were reportedly no signs of trauma to Woo’s body, and her cause of death remains unknown at this time. Sources added that Woo had been acting erratic in the days leading up to her disappearance, and seemed despondent about her relationship with her husband.

The family has lived in Frisco for less than a year.

During an interview with Brandon Woo earlier on Thursday, the husband and father insisted that the couple was not having any family problems that would have prompted her to leave. “She’s a loving mother, a great wife. She’s the most stable person you could ever meet,” he said.

Brandon Woo (Gabriel Roxas - CBS11)

Brandon Woo

Since the mother and her children disappeared on Monday, investigators had been trying to track down where they may have gone. Surveillance camera video showed them at a Walgreens store near their home, and credit card records had placed them at a McDonald’s restaurant a short time later. Woo’s cell phone was left at home, and her most recent calls had been to church members.

A medical examiner will now determine the cause of Woo’s death. The autopsy is expected to be completed next week.

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Meanwhile, a stunned community has been reacting to the Thursday evening discovery. “We are doing all we know how to do right now — a lot of prayer, tons of prayer,” said Carol Spencer of Stonebriar Community Church. They sent Sunday school teachers to the hospital to be available for the children and their father. “We’re doing all we can for this family. Such a sad situation for all of us. Our hearts are just broken.”