The 58-year-old man died after falling out a window at Palmerston North Hospital.
"She deliberately cut it in a way to gloat at how much she was taking off."
Police have cordoned off streets in the suburb of Highbury
The driver did not stop when they collided with the woman, instead completing their U-turn and driving off.
A spokesperson for Mercury's contractor Vestas confirmed no one was injured.
The incident occurred at around 2:30am on Saturday morning.
The driver is now in police custody.
Photographs on social media show an officer crouched behind a vehicle, aiming a gun.
"Who makes these ridiculous decisions?"