The car then went over uneven ground and it was apparently catapulted into the air and ended up crashing into the roof of a neighboring barn about 3 meters (10 feet) off the ground.
The boy was seriously injured, the police statement said.
The driver was an unidentified 42-year-old man, and his wife was also seriously injured. Their two sons, ages 11 and 12, and a 13-year-old passenger were also on board, who like the driver emerged with minor injuries.
Dozens of firefighters, as well as a dozen ambulances and two rescue helicopters were among the emergency services deployed in response.
Images from the scene showed rescuers cutting through the roof, and wreckage of a playground that the car ran through. The car had to be removed from the roof with a crane and was carted away by police. An investigation was underway.