Soafa Niumagumagu has been found guilty of attempting to murder his ex-wife Puapuaga Matamua by stabbing her multiple times outside her workplace after she left him for another man.

He could be heard threatening to kill her as she struggled and called for help in the carpark of Oji Fibre Solutions at Māngere Bridge on June 20, 2019. Niumagumagu had been waiting by her car as she finished a shift, just weeks after she ended their marriage.

A jury has also today found Niumagumagu guilty of the manslaughter of Sagaia Kaisala after a trial in the High Court at Auckland today.

She was struck by his car minutes after she rushed to help her colleague Matamua stop the bleeding from stab wounds.

Niumagumagu has been found not guilty of assault with a weapon against Abdul Riyaz.

Riyaz was a colleague of Matamua's who had tried to chase Niumagumagu away after the stabbing.

Niumagumagu will be sentenced on August 2.

The jury heard from more than 15 people who gave evidence, including witnesses, experts, police officers, colleagues and family members.

He was "beside himself with grief" and felt abandoned after his wife of nine years and mother of their daughter ended the marriage on June 7, 2019, defence lawyer Sharyn Green said.

His colleagues noticed he started smoking at work. Some told the jury they had tearful conversations with Niumagumagu about his marital meltdown.

He told colleagues of his upset and his desire for violence. He referred to shooting or stabbing his wife.

He appeared by Matamua's car as she finished a shift at the packaging factory on Mahunga Drive a couple of weeks later, armed with a sharpened piece of steel.

He stabbed her head and neck multiple times, saying 'I'm going to kill you.'

Matamua struggled and yelled for help. Her colleagues saw her face "dripping with blood".

Kaisala was among the first to rush to Matamua's aid, helping her to stop the bleeding and sat her down on the steps of the smoko area.

Meanwhile Abdul Riyaz was among a group of men who chased Niumagumagu's car out of the carpark and down Hastie Ave, trying to get him to leave.

He threw rocks at his car. A truck driver saw the commotion and tried to block Niumagumagu from driving away. He succeeded for a short time but Niumagumagu broke free, driving back towards Riyaz who tried to run out of the way.

He was hit by the car and flung in the air, witnesses said. They were shocked he survived.

But the violence didn't stop there.

Niumagumagu made his way back to the Oji's carpark at speed, the court heard.

People were jumping out of the way - running behind trees and buildings fearing for their lives, witnesses said.

But Kaisala couldn't run fast enough. She was hit by the car and propelled into the back of another nearby stationary car, before she fell to the ground dead.

Despite colleagues performing CPR, she died before an ambulance arrived.

Niumagumagu then fled in his damaged car which he soon abandoned.

CCTV footage showed him walking towards Māngere Town Centre where he got in a taxi bound for Papatoetoe.

After being arrested, he confirmed to Counties Manukau detective Shannon Barnett he had stabbed Matamua.

"He said to me: 'You know, she was off seeing someone, I was working hard doing all this overtime and she was off seeing him'," he said.

"It was the stupidest day of this man's life," said Green.