A woman is accused of driving her car into a mother and her two kids – killing one of them – and then speeding away during a celebratory festival in Michigan.

And police maintain she committed the crime and was driving without a valid license.

Tammy Sandoval, 55, has been charged with one count of operating a vehicle while license suspended, revoked, or denied causing death – and two counts of operating a vehicle while license suspended, revoked, or denied causing serious injury, according to Wayne County, Michigan, court records.

The Livonia Police Department announced that Sandoval has also been charged with failure to stop at the scene of an accident resulting in death and two counts of failure to stop at the scene of an accident resulting in serious injury.

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On Sunday, June 29, at about 10:45 p.m., Livonia police officers responded to the area of Lyndon Street and Merriman Road, where the Livonia Spree festival was going on. Investigators learned that Tia Robinson, 28, and her two twin children had been hit by a vehicle while crossing the road.

“Due to the time of day, traffic signals were flashing red for Lyndon and yellow for Merriman,” the Livonia Police Department announced in its investigation. “The mother and her children were struck by a vehicle that subsequently fled the scene. Witnesses at the scene removed the injured children from the roadway.”

Khalil Robinson, 3, later died from his injuries. Tia Robinson, the mother, and her boy”s twin sister were critically injured, police said. The family found it hard to believe how such a tragedy could occur.

“All they wanted to do [was] go and have fun at the carnival and the fireworks,” said Regina Robinson, the children’s grandmother, according to Detroit-based Fox affiliate WJBK.

“Why would anyone keep going without stopping, trying to see if they’re okay, and can they help?” she added. “Can they save them instead of driving off acting like they didn’t hit anybody?”

The twins’ grandfather added that it is the “first tragedy” in his family.

“I have no idea step-by-step, day-by-day, and this is the first day, so there are going to be long, long days coming,” Michael Robinson told the outlet.

He also remembered his grandson as a “special little child” who loved to dance.

“He would always go and take stuff to his sister, so if I gave him a piece of candy, he would take one for his sister and take it in there to her,” the grandfather said. “He was very loving toward his sister.”