"Police bailed him to this address with a range of conditions, which included that he stay there with a 24-hour curfew," Mr Bennett said.
"Child, Youth and Family had appropriate steps in place to monitor him, including round the clock supervision until his next court appearance.
"Unfortunately, there was a brief opportunity for him to abscond and he took it."
The agency would not say how the opportunity arose.
"When he is found, he will appear in court and CYF will ask for him to be remanded to a secure residential facility," Mr Bennett said.
The teenager left the scene of the crash on Saturday in a car that police believe he was racing against moments before the collision.
He was arrested after family members brought him to police later in the day.
A 17-year-old from South Auckland has been charged with dangerous driving and will appear in the Auckland District Court this week.
A friend of Mr FitzPatrick's, Kermath Davies, 23, said it was upsetting to learn the youth had fled.
He thought the teenager must have had "a moment of realisation" and took his chance to get away.
"But at the end of the day it's probably going to get him anyway because [what happened] is on his conscience."
Mr FitzPatrick was to have taken part in the Cannonball street-legal car rally which started hours after he died.
Mr Davies said Mr FitzPatrick was a legal "car performer", and his death showed the consequences of racing illegally.
"He was trying to take a legal way and race, and they did it the opposite way and crashed into him."
