"The rider lost control of the motorcycle, slid across the road and collided with a road sign and culvert, sustaining serious injuries."
He was flown to Gisborne Hospital by the ECT rescue helicopter and transferred to Waikato Hospital for intensive care on Friday night.
After the crash, SH2 was closed for more than an hour with no alternative routes available and traffic backed up for about 5km on either side of the crash scene.
The Serious Crash Unit was investigating, with police seeking witnesses who may have seen Mr Mills on his black Ducati motorbike before the crash.
Mr Brown said police were disappointed the crash appeared to have been "almost an exact repeat" of another motorcycle crash on SH50 last month, which saw Peter Randall Papa, 30, of Pahiatua, killed on impact when he lost control of his motorcycle and collided with an oncoming van.
"Both crashes were entirely preventable, and whilst we acknowledge that many bike riders seem to enjoy riding on our windy roads, they still need to drive to the conditions and watch their speed," he said.
In a separate incident, police were also "horrified" when they clocked a man riding a motorcycle at 218km/h on SH5, on Sunday morning.
"This is just plain stupid, and in light of the crashes we have had recently, we would expect more from the self-employed man in his 50s."
Mr Mills' death brings the region's road toll for this year to three.
Five of the 20 deaths on Hawke's Bay roads last year were motorcyclists.