Police have said tasers had to be used on the 29-year-old who died in custody three days after his arrest, for the safety of the police officers involved.

Superintendent Karyn Malthus, Auckland City District Commander, said about 1pm on Sunday police were responding to reports of a man attacking an elderly man on Beresford Street, Freemans Bay.

From the Eagle helicopter it was observed the 29-year-old kicked the elderly man five or six times, essentially until he was unconscious, she said.

"This was a significant and volatile" violent incident, she said.

"It took four police officers to restrain him," she said.

The first two uses of the taser were ineffective, the second two were effective, she said.

If they had not used the tasers the two police officers could have been seriously injured if not killed, she said.

"It would be fair to say that they are traumatised."

Police say the man was transported to the Auckland Police Custody Unit in an agitated state and that he continued to resist police efforts.

He was taken to hospital where he died yesterday morning.

Police were called to the man's address the day before the incident and were reviewing that as well as part of the investigation, Malthus said.

Police had spoken with the deceased's family and were offering support.

Eyewitness details

An eyewitness previously told the Herald the man was acting like a "wild animal" before he was tasered multiple times by police on Sunday.

The man had allegedly attacked an elderly person in Freemans Bay outside a residential address.

"He was out of control," the witness told the Herald.

"He was resisting arrest and he came at the cops as well, he was told to bloody get on the ground and he didn't, so they tasered him."