Questioned over reports from neighbours of "a lot of commotion" and a man yelling that he had killed the unconscious man, Mr Frew said there was no evidence of an assault or altercation of any kind.
Officers had "spoken to quite a lot of people", he said, and "nothing we ascertained indicated anything other than what we tentatively believed, which was that it seemed as though it was a medical event".
"As far as we can gather the first report we had indicated there was disorder," Mr Frew said.
When police arrived at the scene, they found the man unconscious in the street and began CPR. They were shortly joined by ambulance staff.
Investigating officers arrived shortly after and "started piecing together what had happened".
"From that there's no indication that there was an assault or a disorder that in anyway related to the medical event," Mr Frew said.
He put reports of a commotion or fight down to the shouting and distress of those close to the man after he collapsed on the street, "people being concerned about the man's medical condition".
Earlier, a neighbour, who did not want to be named, told the Herald she heard "a lot of commotion" on the street last night.
"I think there was a party and there was a lot of people there standing in the driveway," she said.
As she heard sirens blast past her house, she and her husband went to have a look.
"I saw a man lying in the driveway and a policeman frantically trying to resuscitate him.
They began to walk away, feeling it was disrespectful to watch, and then heard a man yelling: "I killed him."
"I was really concerned and frightened," she said.
She could hear "lots of crying from the house".
"You can hear people wailing," she said.
She didn't know what had happened to the man, she said, but described the street as usually "really good" with such an incident happening "out of the blue".
Another neighbour, who did not want to be named, said she was unaware about what happened last night, however felt unsafe in the neighbourhood.
"Our neighbours fight all the time and [are] always yelling and swearing at each other," she said.
"It's unbelievable.
"It makes you feel unsafe."
Police are awaiting the results of a post-mortem examination.
A scene guard was in place around a house on Hokianga St, close to the intersection of Raglan St, this morning.
