Policing Manager Inspector Brent Crowe urged drivers to take more care, especially on rural roads and highways.
"While the full circumstances of last night's crash are yet to be determined I can say that all too often police are attending serious crashes that are avoidable," he said.
"Factors such as fatigue, alcohol, speed, young drivers and rural roads are all being considered in this case and often combine with tragic and ongoing outcomes."
Police have extended their sympathies to the friends and family of the victims.
A tribute to Thor was posted on Facebook by the Defence Force's No 34 Squadron South Waikato cadet group stated: "It saddens me to announce the untimely death of one of our beloved cadet Thor Sullivan and his brother Hape Sullivan Taken from us all so suddenly following a car accident Friday evening.
Six months ago this fine young gentleman came to me and told me he wanted to join No34 (South Waikato District)Sqn ATC as one of this Units first Cadet Corps Cadets. I was so proud to welcome him into my Unit as he talked about wanting a career in the Army.
"Officers and cadets from No34 Sqn and New Zealand Cadet Forces would like to extend our most sincere condolences to the Sullivan family.
"A funeral service for Thor and Hape will be held Tuesday, more details of the service to follow."
