A 14-year-old is set to appear in Youth Court on 81 charges after a string of "serious" incidents in Christchurch last week.
Superintendent Lane Todd said the charges include assaults with intent to injure, unlawfully takes motor vehicle, aggravated robbery and theft.
Police said a helicopter was used to safely find the 14-year-old.
Three other youths have also been arrested and will be dealt with by Youth Aid.
"Police are confident that the four are allegedly responsible for recently reported incidents of vehicle theft and assaults in Christchurch City," Todd said.
He said police are pleased to have quickly tackled a "significant run" of offending by a small group of young people.
"However it's hard to see these apprehensions as anything more than an inevitable end to a story that started long before any offence was committed," he said.
"It's very rare that youth offenders come out of the blue. We encourage communities to reach out to police if they're seeing concerning behaviour amongst their young people."
Police are working with Oranga Tāmariki and the Ministry of Justice to address the drivers behind youth crime, they said.
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