Enquiries were underway to determine whether alcohol was also involved, Sergeant Shaun Palmer of Waitakere police said.
"We now have a family who are devastated, they've received news this morning that will change their lives forever, and we have a community who are grieving.
"This is the awful reality of the combination of youth, cars and speed and our thoughts are with the boys family."
Police said Ethan's family had been advised and were being assisted by victim support.
The site was blessed by a local kaumatua and the road reopened.
Police this afternoon said a serious crash unit investigation was ongoing and it would be at least several weeks before the exact circumstances of the crash were established.