"We had a quiet night and he went to sleep early. I checked in on him that night - as parents do sometimes," Mrs MacKenzie said. "I heard our dog making a bit of noise and I knew Luke was getting up to go to work."
She lay in bed, listening as he drove off. "Then I heard the sirens ... and I thought, 'I hope that's not my boy'.
"I saw the police walking up my driveway later and it was heartbreaking. It [news of a family death] is not something you want to hear."
The driver of the other vehicle was picked up by another motorist.
Police later found him and took him to Middlemore Hospital. They are still to interview him and have yet to determine whether any charges should be laid. The driver has since been discharged from hospital.
A police spokeswoman said staff were still to determine the cause of the crash, but they had received a witness report that following the crash, the driver flagged down the motorist who drove him away.
They want to speak to that motorist - thought to be an Asian woman aged between 50 and 60 years old.
Mr MacKenzie said it was an extremely difficult time for the family and particularly for their other sons, Tyler, aged 18, and Ryan, who celebrated his 21st birthday on Saturday.
There was a further blow in that Luke died on his mother's birthday.
"So he will forever never be forgotten," Mr MacKenzie said.
"Luke was a great older brother. The boys knew that if they ever needed anything, Luke was there for them."
He said Luke was very entrepreneurial - he had already purchased a house and wanted to run his own business one day.
Long-time girlfriend Ashley Sheppard could barely speak as she described the man she called her soulmate.
The pair had met as teenagers working at a Subway outlet in Botany.
"We've been together for six years and he was everything I wanted," she said. "The day before Valentine's Day, he sent me a bouquet of flowers with a note telling me to be ready by 6.30pm tomorrow night. We went to dinner and had a great time.
"We had lots of things planned together. We were going to travel and get married. I can't believe it."
Mrs MacKenzie said the family had received huge support in the past few days and were concentrating on their time left with Luke, rather than being angry.
"I'm trying not to blame anyone, but I'm probably still more heartbroken and haven't really thought about it," she said.
"I'm just thinking about Luke. I wish he hadn't been going to work. What makes me angry is that he's not here. He should be home."
A service to celebrate Luke's life will be held in Pakuranga today.
Can you help?
Anyone with information on the crash should call: CrimeStoppers 0800-555- 111 or Counties Manukau police (09) 261-1300.
