Police say the man they fatally shot in Wellington's Newlands on Tuesday had a knife to the throat of the woman he was threatening.
On Wednesday the man was named as Sam Fakalago, who police confirm had gang connections.
Acting Wellington District Commander Inspector Tracey Thompson said when police arrived at the Newlands address they were "gravely concerned" for the person inside the house.
"That is the situation where they had to make that decision."
She said the information police received suggested their response would require being armed.
"For precautionary measure, they were going to ensure they were armed."
It all unfolded at about 3pm on Tuesday when police were called to a family harm incident at Kingsbridge Place.
Inside the home were Fakalago, a woman and a young child. Police wouldn't go into detail about the child's involvement but said they were not injured.
Fakalago attempted to barricade himself and the injured woman inside the property, a stand-off followed and, after failed negotiations, he was shot dead by police.
The woman's injuries were treated at the scene by ambulance staff.
Video given exclusively to Newshub shows police running around the property moments before the shots were fired.
Stephen Walsh lives opposite and filmed the whole police operation unfold.
"They tried to persuade the person inside to come outside, they did that for a long time and gave him heaps of opportunity to do so, but he failed to respond in any useful way at all."
Police used Walsh's property for shelter.
"A marksman was hiding behind my skip with a rifle and he signalled me to go down the back of my house, I heard gunshots from there."
Today gang members remain gathered alongside the police cordon at the scene, members told Newshub they were waiting for Fakalago's body to be removed.
Insp Thompson confirmed the man was associated with gangs.
A police spokesperson told Newshub the man's body was removed on Wednesday afternoon and a post-mortem and formal identification process was expected to be carried out on Thursday.