Millar knew something wasn't right.
"A four-wheel drive had just come down the hill so I thought 'Oh that's odd'. We had opened the door, I don't know why actually, and I just said 'Matthew reverse!' and as I said that there was a big roar."
As Matthew, 19, started reversing, dirt slipped down onto the road dislodging a tree, which smashed into the car, spinning it around, and pushing it into the kerb.
The left front wheel rim broke as it hit the kerb and a branch smashed the driver's window.
"We were actually getting out of the car as the car was still slightly moving," Millar said.
"All I thought about was that the car was going to get pushed straight across the road and over that bank and at that moment I said to Matthew 'We've got to get out.'"
Other than a few scratches on Matthew, Millar said they were unscathed.
"If we had gone 10 feet further ahead that's where that big tree came down and it could have easily gone through the car and pushed it straight sideways. I think it was good Matthew was reversing so when the tree hit us it spun us," he said.
Millar said Matthew was "white as a ghost". "He couldn't even speak, he was actually in shock for quite a while after. He wasn't good."
Millar called 111 but was still on the phone when Constable Julian Trinder turned up. Millar was happy to see him.
Fire crews from Paihia and Kawakawa also went to the scene.
Millar then called his wife and she and their daughter came to pick up him and Matthew.
"They were expecting to see some mud on the road and were horrified when they saw it. They thought 'You walked out of that?' The first lady who got there gave us an umbrella and they were like 'My goodness, there is a car in there?'"
Millar said he was going to work with Matthew that day as his ute was being painted - and is glad he was in the car with his son.