He said it became clear the smaller person was a distressed woman.
"She was just getting wasted," Harvey told the court.
"I'll never forget the scream."
Harvey said he approached, put his car window down and challenged the man, swearing at him and warning he'd call the police.
"The rage in his eyes. I won't forget his eyes. He was angry."
Harvey said the alleged attacker invited him to go ahead and call the police.
He said the man then tried to run, but could only muster a slow meander up the road.
Harvey gave chase, and said he got within about 70cm of the alleged attacker before the man got into a parked car.
The woman was groaning, flat on her back and with blood on her face, Harvey said.
He said he initially believed the woman was concussed.
Harvey said members of the public, including two Indian students, tried to help the woman as blood flowed from her neck.
Another witness described screams of terror and a flurry of powerful punches in the quiet suburban street on Monday, July 29, last year.
"I heard screaming of 'help' and 'stop' and that's when I turned around and saw the victim and the attacker together, on the hill," drainlayer Kian Tuhiwai said.
Tuhiwai said the woman was terrified, and he saw the attacker tackle her, grab her by the hair, then drag her aggressively to a grassy area.
"He held her by her head and after everything happened, he just dropped and let go and released," he told the court.
"Everything went quiet after that."
Tuhiwai said workers on the townhouse development construction site in Westgate Drive were stunned.
"We kind of all froze and didn't know what to do."
Members of the public then rushed to help the woman but she seemed dead already, Tuhiwai said.
He said the attacker then went to his car, got in and performed an aggressive u-turn as another vehicle, possibly a Jeep Cherokee, chased after the attacker.
Tuhiwai believed the attacker left in a silver "people mover" which resembled a Honda Odyssey.
On Friday, another witness told jurors she was walking along Westgate Drive at about 8.20am the day Yang died when a car seemed to pull up behind her.
"I noticed that the car moved in front of me and was driving slow as if they were looking for someone," local resident Casey Armstrong said.
She said she took photos of the car, a Honda Airwave stationwagon, in case something sinister happened and she needed to provide evidence later.
"I'd made it apparent before I continued walking that I was aware of his presence."
Armstrong said she removed her headphones and glared at the driver.
"His windows were tinted, though, and he appeared to be looking down."
At about 8.50am she saw the police Eagle helicopter overhead.
"It didn't really occur to me that anything had happened."
The Crown alleges Li was obsessed with revenge after Yang prevailed in a property dispute the couple had a few years earlier.
The trial continues.
Domestic violence - do you need help?
If you're in danger now:
• Phone the police on 111 or ask neighbours of friends to ring for you.
• Run outside and head for where there are other people.
• Scream for help so that your neighbours can hear you.
• Take the children with you.
• Don't stop to get anything else.
• If you are being abused, remember it's not your fault. Violence is never okay
Where to go for help or more information:
• Shine, free national helpline 9am- 11pm every day - 0508 744 633 www.2shine.org.nz
• Women's Refuge: Free national crisis line operates 24/7 - 0800 refuge or 0800 733 843 www.womensrefuge.org.nz
• Shakti: Providing specialist cultural services for African, Asian and middle eastern women and their children. Crisis line 24/7 0800 742 584
• It's Not Ok: Information line 0800 456 450 www.areyouok.org.nz
