Investigators said officers stopped a vehicle just before midnight and ordered a backseat passenger, identified as 41-year-old Holly Hageman, to get out of the car.
While an officer was speaking with the driver, authorities said Hageman climbed into the driver's seat and sped away.
Police said Hageman was found several miles away in Elk Township after the vehicle crashed into a tree.
She was pronounced dead at the scene.
A 5-year-old child was also found inside the vehicle. The child was taken to a hospital and is expected to recover.
Authorities have not said why the vehicle was initially stopped or whether the driver was facing any charges.
The incident remains under investigation.