Hamilton police say the man who died after being restrained by officers was known to them.
The incident happened in Dinsdale in the early hours of this morning, when the man went to the home of his former partner.
The woman's told police he was drunk and got into a struggle with her current partner.
Police have told a media briefing the man died while in handcuffs at the property.
The house has been cordoned off while police investigate.
Photo: NZ Herald