The Armed Offenders Squad are at a Lower Hutt suburb following reports a man was shot.
The reported shooting happened about 2.15pm at a property on George St, in Stokes Valley.
Police say the alleged shooting is a "family harm incident" and there was no second victim, as earlier thought.
A man is still in a serious but stable condition in hospital, said Inspector Scott Cooper.
Police are making inquiries to locate the offender but don't believe they are a risk to the public at this point.
Police have cordoned off the scene while they carried out inquiries.
Police understand all parties are known to each other.
Roxanne Caldow was walking down George St when she heard the gunshot go off and saw two people run out of a nearby house.
"I saw the young gentleman run out and then the woman, and the gentleman was saying 'mum, mum, get out of the house.'"
Caldow said the shot sounded like a door being slammed shut.
"It was quite loud and it echoed through the valley.
"At that stage I was actually quite frightened and yeah, just heard them asking for help and I just rung the ambulance and the police for them," she said.
"It was a freaky situation to be in ... I'm pregnant and I didn't want to get hurt by anybody."
Stokes Valley resident Kathy Fahey said she was heading out of her driveway about 2.15pm to pick up her daughter from school when she spotted a woman "crying hysterically".
A man on a bicycle stopped Fahey and told her to keep traffic from going up the road.
"He says 'can you please hold the traffic down the road, my mate's been shot'."
Fahey was able to collect her daughter from school before she watched the man talking with police, and saw police dogs being deployed.
She said the AOS looked like they were packing up now.
Forty-three South Island co-ed principals have asked the national body to intervene.
