Judge Tony Fitzgerald told the boy that although he was probably "horrified" by his action, he would have to live with it for the rest of his life.
He said there was no sentence he could impose or court order he could possibly make that would lessen the heartache Mr FitzPatrick's family had to endure.
The boy was apparently remorseful and had said he wished he had never got into the car.
At the time of the collision, he was already under a supervision order and banned from driving.
Yesterday, the Auckland Youth Court heard that the teenager had been visiting a friend and, with his cousin, got into a Subaru Forester that had been stolen a few hours earlier and raced another group through the streets of East Auckland, reaching up to 160km/h.
He eventually lost sight of his friend and did a u-turn to go back and look for him.
But when the friend went racing past, he gave chase and went through a red light at the intersection at Carbine Rd and the Southeastern Highway, colliding with Mr FitzPatrick.
The court was told the teenager had spent three of the past four years in youth detention homes and had first come to authorities' attention when he was only a 2-year-old.
His early life was marked by abuse and neglect, then in later years he developed out-of-control behaviour, Judge Fitzgerald said.
Mr FitzPatrick was enjoying life and was in a "good space" at the time of his death, his funeral service was told. He loved music and was a natural at computers, which led him to complete a diploma in IT at AUT.
Mr FitzPatrick's parents declined to comment.
The teenager was put into Child, Youth and Family custody after his arrest but escaped from a supervised home.
At the time, CYF operations general manager Grant Bennett said the boy was supposed to be monitored constantly but took advantage of a "brief opportunity".