The sisters have the same last name as the decedent from the hit-and-run article, implying that they are his daughters. Further, Avery Stone spoke of driving a fancy new sports car, similar to the one described in the hit-and-run article. 

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Therefore, Krista Swanson poisoned Avery Stone with the help of her sister, TSA Agent Kelsey Swanson. Avery Stone was the driver who killed their father in a hit-and-run.