At least three members of a family were killed and an infant critically injured after a speeding dumper overturned on a car early on Wednesday here, a police officer said.A motorist informed the police around 1 a.m. about the accident in which the dumper laden with sand, while taking a U-turn, overturned on the Audi car in Rohini area, Deputy Commissioner of Police S.D. Mishra told IANS.The deceased have been identified as Sumit, 29, his mother Ritu, 59, wife Ruchi, 27. His three-year-old son is critically injured and undergoing treatment. They were returning from a family function when the incident happened."The driver of the dumper managed to flee from the spot. A hunt is on to nab him," Mishra said.