"This incident is still under investigation by the serious crash unit who are working to determine what occurred."
Mrs Grace said initial indications showed Mr Rose was travelling north on Purangi Rd, towards Cook's Beach, when his vehicle failed to negotiate a bend and went through a wooden barrier immediately before the bridge.
The car flipped as it dropped into the stream, she said.
Police were waiting for toxicology results to determine if alcohol played any part in the crash and were checking the road-worthiness of the vehicle, as it had not been registered or held a warrant of fitness since 2012.
"While expressing the police's sympathies to Mr Rose's family, it's still important to highlight the need for both vehicles and drivers to be fit for the road at all times.
"To not be at your best or by being behind the wheel of a vehicle that is not certified as road worthy can put your life, and the life of other road users at risk and it's simply not worth it," Mrs Grace said.