"If I had known what she was going through, I would have tried to help her or reach out to her," another friend says

By Harriet Sokmensuer
Updated April 22, 2016 05:10 PM
Credit: Frisco Police Department

Christine Thi Woo, the Texas mother who was found dead in her SUV with her living children beside her last month, committed suicide, PEOPLE confirms.

According to the Collin County Medical Examiner, Woo’s cause of death was suicide through overdose, police tell PEOPLE.

Before she killed herself, the mother of three was caught on camera at a local Walgreens buying a bottle of sleeping pills. Police say the bottle of sleeping pills was empty when Woo was discovered.

Friends of the 39-year-old tell PEOPLE that Woo was a devoted mother and seemed happy and positive.

“She was very lively when you spoke to her. She was an extremely sweet, gentle soul,” Elle Bonner, Woo’s neighbor says. The two lived in the east Frisco neighborhood Lawler Park.

However, Quynh Chau Stone a friend of Woo’s, said she seemed depressed when they spoke a month before she died.

“I could tell that she was struggling and depressed,” Stone says. “I could hear a stumbling in her voice. I think she was … just trying to find her place in life.”

Eileen Tan taught Woo’s children – two girls, 5 and 1, and one boy, 3 – at 7 Notes Yamaha Music School, where Woo and her family would spend their Saturday mornings together in class. She says the mother-of-three didn’t seem unhappy.

“She was always smiley,” Tan, the founder of 7 Notes, tells PEOPLE.

Tan says Woo would take her eldest daughter to piano lessons and join her in class while her husband, Brandon, would take the youngest children to their lessons.

Earlier this year, Tan says Woo pulled her children out of classes for two weeks but signed them up again. Tan says maybe that was a sign she needed help: “If I had known what she was going through, I would have tried to help her or reach out to her.”

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On March 28, Woo and her children were reported missing by her husband. Three days later, she was found dead in her silver SUV parked in a Target parking lot in McKinney with her children beside her.

According to a Frisco Police Department press release, Woo did not mean to harm her children in anyway: “there was no deliberate plan by Woo to harm her three children.”

The children were taken to a local hospital to be treated for severe dehydration, police say.

The Friday after her body was found, Frisco Moms Care, a local parenting group, held a candlelight vigil. Cate Biggs, founder and president of the group, says local mothers wish they could have helped Woo.

“If a mom is feeling sad, overwhelmed or alone or like they need a sisterhood or a friend that’s part of what we do,” Biggs says. “We’re here to help and I guess part of me thinks what if? What if we could have saved her.”