The child was hit by a vehicle backing out of the residential driveway at 233 Mill Road, said the statement from Chief of Police Leon Krolikowski.
"The accident remains under investigation," Krolikowski said. "No additional details will be released at this stage of the investigation. We ask that the family is given the respect and support they need during this very tragic time. The family is in our thoughts and prayers."
The accident occurred at about 4 p.m. Friday, police said.
The child, who was not identified, was taken for treatment to Norwalk Hospital, where he died.
New Canaan police did not say who was driving the car or any other details of the accieent.
The Darien Police Department said via Twitter that its Accident Investigation Unit responded to the scene to help with the investigation, which is continuing.
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