Welch, the driver of the car, was following as a safety measure intended to prevent other vehicles from endangering Hunter.
Though the details of the crash aren't clear, it appears Hunter fell as he was going around a corner without Welch realising.
When Welch saw the longboarder on the road he swerved into a bank to avoid hitting him, but bounced off, hitting Hunter.
Hunter's family did not blame the driver, calling the death a "freak accident".
He was regarded as one of New Zealand's best longboarders and had aspirations to ride professionally.
Welch's lawyer Michael Bott, said the key message was that a young man had died while participating in an extreme sport he loved.
"In this situation, a young man drove a car too close behind. Something went wrong and the inevitable occurred," Bott said.
"There are no winners, my client's been through the mill. As I say, it's just a tragedy."
Bott said Hunter's parents had shown the "utmost sympathy" for Welch.
Welch and Dageville had "been through a massive amount of trauma".
"Their grief is real and profound, and the court could see that today - that's also in part why the parents of the deceased also feel profound sympathy for them."