Aden S. Martin, who owns a farm in Huron County, told CBC News that Mark Streicher, 45, his wife and eight children weren't far from their home on Highway 9 when the buggy was struck.
Martin said it was smashed to pieces.
Other residents in the area confirmed to CBC News that Streicher and his wife have 10 children and the collision happened almost right in front of the family home.
Wellington County OPP said two children, aged four and six, were airlifted to hospitals in London and Hamilton. They are in critical but stable condition.
The rest of the family members did not suffer serious injuries and have all been released from hospital.
One neighbour said he often got fresh eggs from the Streicher family, who are Mennonites.
Investigators said a 2012 Volkswagen GTI was travelling northbound on Highway 9 when it collided with the buggy that was travelling in the same direction.
Tire tracks spotted by CBC News indicate the car left the highway.
After the collision, Martin collected pieces of wood from the buggy, as well as the family's belongings, including a shoe and a pink disposable diaper. Martin also had a piece of the VW symbol from the vehicle.
Both the driver and the horse were not hurt in the crash. Police have not yet announced whether any charges will be laid in the crash.
It isn't known if the buggy involved in the crash had a slow-moving vehicle sign or reflective tape affixed to it.
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