Porirua Police say they're "deeply disappointed" by a violent punch-up at Creekfest, a family event, on Saturday.
"A video on social media shows a disgusting act of violence toward a young woman at this family-friendly event, attended by about 32,000 people," says Kapiti Mana police area prevention manager Senior Sergeant Grant Ferguson.
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The video shows a young woman approach two other young women, making an accusation that isn't completely audible on camera.
The two women, one of them wearing a red top that says 'PORIRUA', then lay into the lone woman, kicking and punching her, and pulling her to the ground by her hair.
Even when the woman is curled over and covering her face, they continue to kick and punch her in the head. Onlookers are heard yelling as they video the attack.
Snr Sgt Ferguson says the organisers "worked very hard" to produce a quality day, "and stay true to the anti-violence, healthy living and family theme".
"I know I speak for the organisers, sponsors and supporters of Creekfest, when I say I am deeply disappointed and saddened by what occurred.
"This is not what the day was about, and not what or how we want people to remember Creekfest."
The official website describes the annual event as a "fun environment" to "raise awareness of programmes and services available in the region to achieve better health and wellbeing outcomes".
Festival organiser Liz Kelly, from Porirua Whanau Centre, told Newshub the incident is disappointing and doesn't reflect the positive vibe of the 32,000 people who attended the festival.
"It had nothing to do with the Creekfest and it's really unfortunate. My heart goes out to the victim and her whanau."
Ms Kelly says despite its reputation Porirua is generally a positive community.
The festival has been running for 12 years and there's never been any violence. It promotes healthy living, connecting whanau and anti-violence.
"I think we've made huge in-roads and it's just a shame these two people have put this blight on the weekend," Ms Kelly says.
Hundreds of Facebook comments criticise the women as "gutless" and "cowardly".
"It's encouraging to know more and more people do not and will not accept violence in our communities," Snr Sgt Ferguson says.
Police are investigating the incident and hope to "hold those involved to account in a timely manner".