A year on from the bus crash which claimed the life of Chris Tobin and his baby son Jack, it has emerged the tragedy could have been caused by a family dog distracting the father of five.

Tobin, 51, and Jack were killed, and Tobin's 3-year-old daughter, Elle, was critically injured after the car the Auckland man was driving crashed into an NZ Bus double decker bus on Mt Eden Rd last July.

Tobin died at the scene, while Jack had his life support machine turned off several days later due to the severity of his injuries.

The crash happened on the 31st birthday of Tobin's partner, Olivia Kronfeld; the mother of the couple's three children Elle, Vivienne and Jack.

As family awaits a Coroner's hearing into the tragedy, NZ Bus has revealed to the Weekend Herald that a distraction caused by the Tobin-Kronfeld's family dog – a huntaway called Fox - may have led to the crash.

"Our understanding is that the police's best guess was that the driver was distracted by the dog in the back seat, missed a turn and drove into our double decker," a company spokeswoman said.

"It is a very tragic accident and our hearts go out to the family of the deceased."

The scene of the fatal crash on the corner of Mt Eden Road and Bellevue Road in Mt Eden Auckland. Photo / File

The driver – who was cleared of any responsibility – was deeply affected by the tragedy and isn't back driving full time.

Police were unable to comment on the case, including the comment from NZ Bus on the possible distraction caused by the family dog, as the file was now before the Coroner.

Tobin's family also hadn't heard anything from police about the potential role of Fox in the crash.

But Kronfeld's mother Fiona Keilman said: "I actually wanted to get rid of the dog straight after the accident. I was anti the dog, because I fully had the same thought [that it may have contributed to the crash]. It's like do you want the dog or do you want Jack back?"

Now whenever the dog travels in the family car it is tied up in the boot.

Keilman said authorities had not been able to tell them if Tobin had suffered a medical event pre-crash or the outcomes of toxicology tests. But she said Tobin had not been drinking before the crash.

Keilman said their hearts went out to the bus driver.

"We thought of the bus driver at 3pm on Olivia's birthday," she said. "We thought he would be traumatised too. Olivia feels empathy for the driver because she knows what he's going through more than any of us would ever know."

A year on, Kronfeld's mother said the "waves of pain are less but the first six months was a blur".

"The pain has been so unbearable for Olivia at times she has not wanted to live," Keilman said.

"Chris, she has dealt with but Jack was her everything. She feels guilt and she doesn't want to live because she misses Jack."

Elle Tobin survived a car crash in Mt Eden that killed her father Chris and her brother Jack last year.

The decision to turn off the life support machine for baby Jack was devastating for the young mother, Keilman said.

"Jack's injuries were horrific. His head was severed from his spine, there was no hope he would ever walk or have a quality of life," the grandmother said.

"After Olivia made the decision to turn off the machine, she cried and cried."

On the day of the accident Tobin had taken the day off work to celebrate his partner's birthday.

About 3pm, Keilman asked Tobin to drop Kronfeld's father Greg back to work at a construction site in the Viaduct.

Elle wanted to go for a ride with her dad and Jack, who had recently learned to walk, toddled out towards the car.

Both children were buckled in, and then the family's huntaway dog Fox jumped into the back seat. On the way home Tobin lost control of Keilman's white Nissan Cube which crossed the median strip on Mt Eden Rd and collided with the bus.

Keilman said Elle – whose injuries included "mild" brain damage – doesn't remember much about the crash. But for some time she was worried about how fast any car she was in was travelling.

She said the wee girl – who turns 4 next month – can get fatigued easily due to her brain injury.

Both Elle and Kronfeld's 6-year-old daughter Vivienne – who was not in the car when it crashed - are also receiving grief counselling.

"We have to make sure Vivienne isn't forgotten in all of this," Keilman said.

Chris Tobin and Jack Tobin.

And the family want to thank the public who donated to a Givealittle fundraising page for them, as well as police, Starship children's hospital and the staff from the Honeywell office on Mt Eden Rd who comforted Tobin before he died.

Tobin – who had two sons from a previous relationship – and Kronfeld had known each other for about eight years.

Keilman said the past year had been tough on the family; saying Christmas had been "horrendous", and more heartache was endured on Father's Day, Tobin's birthday, and the one-year anniversary of the tragedy.

Kronfeld has been pragmatic with her daughters.

"She told them Papa and Jack had passed away … but they can still see them in their dreams," she said.

Last week when Keilman drove her granddaughters home from school and kindy, Elle said: "The two seats next to me are Papa and Jack's seats. They can see me all the time. It makes me happy."

WHERE TO GET HELP:

If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call 111.
If you need to talk to someone, the following free helplines operate 24/7:

DEPRESSION HELPLINE: 0800 111 757
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There are lots of places to get support.
For others, visit: https://www.mentalhealth.org.nz/get-help/in-crisis/helplines/