The toddler was almost hit by another vehicle just moments earlier.
The 2-year-old was struck by a car on Mt Eden Rd just after 11.30am yesterday. His elderly grandmother was also hit by the car as she ran out to try to stop him.
The pair had been at a playgroup at St Barnabas Anglican Church and as they left the church grounds to go home the boy twice ran out into the traffic.
The first time, his grandmother managed to grab him, saving him from being hit by a car driven by Thantut Nyein.
"When I got near St Barnabas Church a toddler ran out from the pavement towards my car. The toddler got to about three feet [about 1m] onto the road but on that occasion, an elderly lady was able to regain control of the toddler.
"I had to slam on my brakes. It was very lucky that the toddler did not get to my car."
Shortly after, the toddler took off again and was hit by a Mazda driven by a woman travelling with her own child.
"It appears that as the young boy and his grandmother came out of the playgroup he ran off. She chased after him and stopped him," said Senior Constable Martin Beeby.
"Then he's run out again and she's run to try to stop him and they have both been hit by the car."
As the elderly woman and toddler lay injured on the road, bystanders rushed to help, including other parents from the playgroup.
Mr Beeby said the grandmother did not speak English, but was conscious when emergency services arrived.
Frederick Qiu, who works across the road from the church, acted as a translator between the injured woman, who spoke Mandarin, and paramedics.
"I didn't see the crash, but I heard a baby crying and crying and I went outside. I saw many people crowding around a little child," he told the Herald.
"He was lying on his side, the woman was lying on her stomach. She could not say much. I asked her what happened and she said 'the car hit me'.
"She kept asking for her grandson - I told her he was crying, and that had to be a good sign. I just kept her calm and told her not to worry, that there were many people helping the boy."
It is understood that the injured pair's family arrived at the scene soon after they were struck.
A witness said a woman who knew the injured grandmother came running over: "She looked absolutely devastated."
The child was in a critical but stable condition last night at Starship hospital. His grandmother was recovering at Auckland City Hospital with broken bones and grazing.
Police were speaking to a number of witnesses including parents from the playgroup.
"We are all very upset about it. The police have been taking statements," St Barnabas Church Reverend Bob Hornburg said.
"We all just want to wish them all the best."
Police who attended the incident said the scene was "devastating".
Yesterday was the second day of the United Nations Global Road Safety Week. The week focuses on promoting safety awareness around the most vulnerable road users.
Police were investigating the crash and said charges were highly unlikely.
