Wiremu Puha-Tirikatene, 19 -- Mr Kitto's best friend -- was riding his own motorbike and saw his friend crash.
Mr Puha-Tirikatene had known Mr Kitto since childhood and said his friend "lived his life hard and fast, he lived on the edge".
"There was never a dull moment... he was one of the most genuine and outgoing guys I knew," he said.
The pair spent time together most days.
Mrs Cassidy said her son loved cars and often rode his motorbike.
A tangi for the teen began at Tuahiwi Marae yesterday.
Mr Puha-Tirikatene said family and friends would remember Mr Kitto's cheeky nature and constant smile.
"He was a true brother, we love him very much. He will never be forgotten and we are so grateful for his friendship and love."
Online tributes to the teen also painted a picture of the loss felt by loved ones.
Family and friends sent their condolences to Mrs Cassidy and her daughter, Michelle, and to Mr Kitto's father, Mervyn.
Wendy McKay said: "Andy and Shell my heart aches for you! So cruel so not real!"
Craig Careswell said: "Massive Hugs Andrea.The pain would be unbearable. Our thoughts are with you all at this time."
Patrine Roche said: "Sending you, Mervyn and Michelle all my love."