A father accidentally reversed over his 15-month-old son on his driveway without realising before driving off, sparking a police hit-an-run investigation.
Jamie Ellison has now spoken of his guilt - saying it would be "etched" in his mind "forever".
He said he had no idea his son had left the house while his back was turned, and had been stood next to his car, on his blind side, when he began reversing out of his driveway.
Writing on Facebook, he said he had been taking his two daughters to school, and waved to his young son AJ who had been standing in the window of their home in Cheltenham, Gloucestershire.
When he returned, he found police and ambulance in the street, and was told by his girlfriend that AJ had been found at the side of the road with multiple serious injuries.
He, along with police, assumed his son had been the victim of a random hit-and-run. He climbed into the ambulance and went with his son to Gloucester Royal Hospital, all the time oblivious that he was the one who had hit the boy.
Officers sealed off the road and began combing through CCTV as part of a hit-and-run inquiry - but it quickly emerged that Jamie himself had been responsible.
In the posting, he appeared to suggest that he had received abuse from some people accusing him of deliberately hitting the child.
AJ's two older sisters had not realised their brother was there either, he added.
He called the incident a "horrible family tragedy" - and said telling his other children what had happened had been incredibly difficult.
AJ was now back at home and "recovering well", he added.