They had been talking about what a great year it had been, and they had no idea their beloved son and grandson was no longer alive.
Collier said the loss of her eldest grandson on Monday had been a devastating blow to the tight-knit family, who would gather in Tauranga this afternoon for Hart's funeral.
Hart, 35, became a father to a baby girl about three weeks ago.
"On Monday night she and I were talking about what a wonderful year she has had - two new grandchildren, she won a scholarship, got a new car. All the time Steven was dead and unidentified. We had no idea," Collier said.
"She was sitting out on the balcony, looking at the stars and saying what a beautiful place we live in. That was about 9 o'clock."
At 6.20am the next day, Collier's phone rang.
"My daughter was barely able to speak. She said 'Mum, I've got some very bad news. Steven was involved in an accident'. I said 'Oh, how is he?' She said 'He's not'.
Collier then informed the rest of the family.
"This is the first person we've lost like that. A sudden death is different to a death you were waiting for," she said.
"It just shows how your world can change in a moment. It's always other people's children who get killed in road accidents."
Until now.
Collier said her grandson had always lived in his own little bubble, but now it was younger members of the family feeling isolated.
"My youngest grandson said 'it feels like we are in a bubble and the rest of the world is going past me. The other kids at my school have no idea my cousin's been killed'."
Collier said Hart and his partner were starting a new life together. His partner expressed on social media her heartbreak at his death but did not wish to comment further.
The latest fatalities bring the road toll on Western Bay roads to 14, which compared to 14 deaths for the whole of 2017, and 19 in 2016.
In total, 87 people have died on Western Bay roads since the start of 2013.
On Wednesday, Gisborne man Te Hokinga Mai Katipa, 30, was killed when his car was involved in a crash with a car transporter on SH29 in the Kaimai Range. The crash near the intersection of Old Kaimai Rd closed the highway for several hours.
On Thursday, two others - a man and a woman - died after their car and a fully laden logging truck collided on State Highway 2 near Pukehina.
The car and the logging truck both came to rest down a grassy bank, and the highway was closed for almost six hours. The victims of that crash are yet to be named.
Senior Sergeant Mark Pakes, the head of the Western Bay of Plenty road policing, earlier said the cause of Pukehina collision was still being investigated by the Serious Crash Unit.
Maketu Volunteer Fire Brigade chief fire officer Shane Gourlay and his crew attended the Pukehina double-fatality along with a fire crew from Pukehina.
Gourlay said in his 30 years with the fire service he had attended at least 40 fatal crashes in "his patch".
Gourlay said when and his crew, which included some " newbies" got to the scene one of the deceased was still trapped inside their car.
"These incidents take a huge toll on my crew, and it never gets any easier, even for us old hands, and that's why we're all offered to undertake some counselling, " he said.
"Four deaths in four days is shocking, and it's an unbelievable strike rate. What's really sad about all these fatalities is that these crashes were probably caused by momentary inattention or people taking unnecessary risks.
"I just feel so sorry for all the deceased people's families and what they are going through."
Gourlay said it was really sad that despite all the road safety messages on TV, radio, and newspapers and on road signs the tragedies kept happening.
The impact of road tragedies had a massive ripple effect on police, firefighters, ambulance staff, others assisting at the scene, and the wider community, he said
Gourlay said it was the first fatal crash for the brigade's rookies and it was such a shocking scene. As soon as he could they [the rookies] were replaced by more experienced crew.
Last month the Government announced a $4.3 billion investment over the next three years to reduce deaths and serious injuries on New Zealand roads.
But these safety measures won't come soon enough for the families of the deceased or other motorists travelling on some of the most dangerous roads in this district.
Deaths on Western Bay roads:
2018: 14
2017: 14
2016: 19
2015: 18
2014: 16
2013: 6
Source: Ministry of Transport