Police said the carpark area around the bar was well covered by CCTV cameras and officers were interviewing and collecting footage from the surrounding shops.
A man who works at 123 Karaoke Bar and identified himself only as Richard told the Herald on Sunday that he didn't see the fight, but heard screams as it unfolded.
He said the bar was filled to capacity with about 55 people waiting to take their turn on the karaoke machine.
Richard said the men had not argued inside the bar, but described the incident as "more than a fight".
"It wasn't because they were drunk, I know that. There was an argument because of the partners," he said.
"That guy who is dead, I think it started because of his wife or fiancee."
Two tearful women, who didn't want to be identified, witnessed the incident and returned to the scene yesterday to try to get their car, which was behind a police cordon.
"We're a bit traumatised, we've just spoken to police and gave them a statement. It was a very traumatic thing to see," one said.
Police had erected two scene examination tents - one covering the man's body and another a silver car. A post-mortem examination is expected to be carried out today.
"We are working closely with the deceased's family and remain focused on their well-being and to ensure all available information about the circumstances of their loved one's death is fully investigated," said Alexander.
On Friday afternoon, a man died at his work at Wiri, South Auckland, after a fight with a colleague.
Emergency services were called to the Foodstuffs warehouse about 1pm and found the 45-year-old man in a critical condition.
He went into cardiac arrest and died.
Foodstuffs North Island manager Murray Jordan said the man's family were being supported.
Meanwhile, in Waiuku a teenager suffered critical injuries after allegedly being bottled and stabbed in the head at an out-of-control party in the early hours of Saturday morning.
Staff from the Waiuku Volunteer Fire Brigade found the teen at the Victoria Ave address about 3am with blood pouring from his head.
He was taken to Middlemore Hospital. A resident who lives on Victoria Ave said a crime scene unit had cordoned off part of the street.
He said a number of teenagers lived in the area, and nearly 1000 were enrolled at the local high school.
"There's a reasonable amount of young people, generally they're all pretty good and pretty sensible.
"They're not a bunch of knife-wielding thugs, generally they're pretty respectful of people here," he said.
