That video is bloody horrific, and it's disgusting that these kinds of practices are permissible here. These abuses of power are nothing new for this country and in the past 3 years, there have been efforts from Jacinda Ardern to expand police powers. These include the Covid response bill which allowed for the warrantless searches of Maraes and her implementation of armed policing squads in 2019 following the Christchurch massacre.
In general yes, New Zealand also has a very high gang presence from what compared to many other countries, which has been increasing.