A video that appears to show a gang member beating a teenager in the head has been viewed several hundred thousand times since it was shared on Facebook on Thursday.
The 80-second clip begins with a man in red - apparently a member of the Mongrel Mob - driving a car, asking a teenager in the passenger seat if he'd tried to pinch his vehicle.
"Nah, I was trying to fix it for you," the teen replies.
"What was you fixing, bro? It was just parked up on the side," the man asks.
"Nah, it wasn't going or anything," the teen replies.
"What are you talking about?... There was nothing with it bro," the man insists, before suddenly striking the teen in the head.
"Was there anything wrong with it?" the man asks angrily.
"No. Nothing wrong. Nothing wrong. I'm sorry," replies the teen, covering his face and cowering away from his assailant.
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It's not clear when the video was shot, but it was shared on Facebook page The Bro Hub late on Thursday night. It's since had 294,000 views.
The video is credited to a young man who appears to live in Napier. Many of his public photos show people dressed in Mongrel Mob gear.
It's not clear at this stage if the clip is real or was staged.
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Police say they are aware of the video, and would like to speak to anyone who has information about what it shows - including the victim if the alleged attempted car theft.
"Police take all reports of criminal offending seriously and will follow up as appropriate," a police spokesperson told Newshub.
"We ask that people please contact us if they witness a crime taking place, rather than taking matters into their own hands."
Jarrod Gilbert, gang academic and author of Patched: The History of Gangs in New Zealand, told NZME it wouldn't surprise him if the video was authentic.
"If someone steals a car the ordinary course of action is to go to the police and get it sorted out through the justice system.
"Gangs will take care of it themselves and bypass state channels."
A week ago Hawke's Bay police arrested a number of Mongrel Mob members during the biggest meth bust in the region's history.