Two men from the car, Clarke McCallum and Daniel Rippon, assaulted Mr Kumeroa.
He died in hospital two days later.
Ms Uruamo said she saw a man in a red sweatshirt walking down the street, and saw a car drive past him with people leaning out the windows and yelling something she couldn't make out.
The car pulled over.
Ms Uruamo struggled to remember certain details, but said at some point she saw the same man being pulled out of the back of the car and pushed to the ground.
She did not remember seeing how the man got into the car in the first place.
The two other men punched and kicked him before returning to the car.
"And then . . . I saw the tall guy. He got out of the car and he unzipped his jacket. He had something in his jacket. And then he just walked over and hit the guy with the red jersey."
Ms Uruamo said she only saw the handle of the object, and thought it was a bat. She later said it was an axe, and that the "tall guy" had hit the other man on the head with the blunt side.
Ms Uruamo also described to the court seeing a female with a ponytail yelling out of the car window when the car first pulled up.
"When I close my eyes I think about that girl in the back. I can see a ponytail, fringe, dark. And that's it," she said.
She heard female voices yelling, and when the red-topped man was being pulled out of the back of the car, she saw a female pushing him.
After the "tall guy" hit the man in the red top with the axe, she heard female voices yelling "get in the car", and saw the two other men pushing and shoving each other as they tried to get in the vehicle.
She said the whole incident took about a minute, "but right now it feels like forever".
The trial continues, before Justice Rebecca Ellis.