John Harvey said it had "never once" occurred to him that it could have such tragic consequences.
"It scares me that I let it happen so many times," Mr Harvey said.
Police serious crash investigator senior constable Greg Taylor said tests showed that drivers were unable to see about 45-55 per cent down the left-hand side of the bus, "making this a hard-to-see area for the driver".
Subsequent to Mahuri's death, extra mirrors had been fitted to the left side of all its 85 Volkswagen school buses nationwide, as recommended by the police.
"It is accepted there is a driver blind spot on vehicles of this sort. However, such blind spots exist with virtually every large vehicle, whether they be passenger service vehicles or otherwise," Mr Taylor said.
Ritchies sent a memo to all its drivers urging them to be on the lookout for children running alongside buses. The same memo was sent to Bus and Coach Association members.
Drivers were advised to stop the bus and speak with the children if they did see them running alongside.
Mr Taylor said the there was no evidence of vehicle fault, road fault or suggestion that speed was a factor in the Hector fatality.
"The incident resulted in the young boy following the bus and as it turned left at the same time, the child has fallen on to the road and the left rear wheel ran over him."
All the children interviewed gave similar accounts of what happened, saying that Mahuri was running backwards, or running forwards and looking backwards as the bus drove around the corner.
Mr Taylor said suggestions Mahuri had hit the front left-hand side of the bus were not substantiated.
"Two adults at the scene recalled seeing the rear of the bus move, like it had driven over something as it was completing the turn into Greenfield Street. None of them realised what had happened until they heard the screams of kids," he said.
Mr Taylor said the driver looked before he drove away from the kerb at the bus stop to ensure the way was clear - "then he felt a bump and stopped".
The driver would have had limited visibility as he looked at the mirrors and the rear view mirrors.
"It is not known if the driver re-checked the rear view mirror as he was making sure his way was clear ahead of him. Even if he had re-checked, with the limited visibility it may not have shown what was unfolding anyway."
Mr Taylor said Mahuri either tripped or fell, or possibly a combination of both, then the rear wheels of the bus ran over him as it rounded the corner.
- The Greymouth Star