Horton said he arrived at the crash scene less than two minutes after the accident to hear his wife screaming in the darkness and to see his son's friend and the family dog scrambling up the bank. His son Silva was trapped inside the submerged station wagon.
He tried to dive down to the vehicle, which was nose down but with the tail lights burning more than 3 feet (1 meter) below the surface, he told the Dominion Post newspaper.
"I tried to get down and get him but I couldn't - it was just too deep. And Vanessa was going under," Horton told the newspaper.
"I made a call to pull my wife to safety. I looked back and I could see the tail lights but it was too far and I couldn't get him," he said.
"Instead of going down and risking my life as well as my wife and son's, I chose to take V(anessa) back and sat on the shore praying. It was all I could do," a distraught Horton said.
Police and fire officers also were unable to rescue the boy from inside the vehicle.
Mid-Central police spokeswoman Kim Perks said Monday it was a very tough call for Horton. "I would certainly not have wanted to be in his shoes."
Senior fire station officer Gary Wilson said the water was dark and murky and firefighters struggled in vain to reach the car.
"We tried everything but to no avail," Wilson said.
Divers recovered the boy's body on Sunday.
Written by Associated Press