A 6-year-old Texas girl with an incurable cancer said she had dreamed of becoming a police officer, so the Freeport Police Department decided to make her an honorary officer for the day – and the chief of police broke down while swearing her in.

Abigal Arias has a stage-four Wilms' tumor wrapped around her aorta. She went into remission for five months, but then the cancer spread to her lungs. Abigail's doctors don't know of any treatment or chemotherapy that is able to cure her, CBS affiliate KHOU-TV reports.

Despite having an incurable cancer, Abigail has not given up her fighting spirit. Freeport PD

"That just devastated us," her father, Rueben Arias, said. Abigail's mom, Eileen, said the family's "greatest struggle is saying no to fear."

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"We're strong in our faith," her dad said. "We believe in God. The doctors can say what they say medically, but we know that God is the one that has her destiny in his hands."

Abigail thought up a good way to combat what she calls "the bad guys" in her body that are making her sick. She wanted to fight them by becoming a police officer.

The 6-year-old first met Chief of Police Ray Garivey in December and told him about her dream of becoming a cop. "I said, 'We're going to make that happen,'" Garivey said.

The department invited Abigail to be sworn in as an honorary officer Thursday, under one condition: Garivey made Abigail make a promise in her oath. "I now and forever promise to keep fighting the bad guys until all my cancer's gone," she said.

The chief couldn't hold back his tears while swearing in the terminally ill girl. He was overcome with emotion as Abigail received her badge, which she wore on her tiny police uniform.

Abigail was sworn in under one condition – she promised to never stop fighting. Then, she got to fulfill her duties as an honorary cop for the day. Freeport PD

Abigail got to sit in a police car and eat an officer's treat – a doughnut. She said becoming an honorary officer made her feel "neat" inside. "I felt excitement and all love," she said.

After her day as an officer ended, Abigail swore she would keep her promise for Garivey. "I want to help the bad guys go away," she said. "I want to help this cancer go away in five seconds."