A mother and child were killed after a car mounted the pavement and smashed into pedestrians before crashing into the wall of a Jaguar dealership.
West Yorkshire Police believe they were pedestrians and were hit by the car after it left the road.
A woman and a child, believed to have been pedestrians who were hit by the car before it collided with the wall, were found injured at the scene.
Both were pronounced dead a short time later, a force spokesman said.
The spokesman said the driver of the Audi was arrested.
He is being treated for injuries which are described as serious but not life-threatening.
Detective Inspector Paul Conroy said: “This is an absolutely tragic incident, and we are working to support the family of the woman and child involved.
“We have already spoken to a number of witnesses but are keen to speak to anyone else who has witnessed the collision itself or the events leading up to it.
“We would also ask anyone who was in the area around the time of this collision to check their dashcam footage.”