By law a child aged 12 or 13 can be held in police custody if they have been charged with a crime that carries of penalty of at least 14 years' jail.
The police spokeswoman said it was later decided the boy would be dealt with through the care and protection provisions of the Oranga Tamariki Act.
"Dealing with youth offending requires a balance between the four principles of public safety - victims' needs, accountability and the welfare and interest of the youth offender," the spokeswoman said.
"Offences are dealt with in line with the ... act. That is, that they are held accountable, and encouraged to accept responsibility, for their behaviour. They are also dealt with in a way that acknowledges their needs and that will give them the opportunity to develop in responsible, beneficial and socially acceptable ways."
Where possible, wider family and iwi are involved in making decisions relating to addressing underlying causes.
She would not comment further as the matter is going through the Family Court.