The drama started outside the Unichem Buchanans Pharmacy.
Witnesses working in the shopping centre said a man drove off with the car boot open.
A pharmacy staff member said she and her colleagues heard "lots of screaming" and went outside to check.
"An elderly couple were loading their groceries in their car. The keys were in the car and this man comes, jumps in and nearly bowls them over while driving away," the witness said.
"It's an awful thing to happen. I feel sorry for them. We bandaged them, looked after them until police arrived."
A shop worker said it was lucky the stolen car did not hit anyone.
"The old lady, she was sobbing her heart out. She was concerned about her groceries because they are pensioners. He just backed out, he didn't care."
The worker said a lot of people came to the couple's aid and took them into the pharmacy.
Another shop employee said he saw a car being driven away at speed with its boot open.
"It's sad as a lot of people work here every day and these things can affect them in many ways," he said.
Photographs taken by witness Darren Boon show a police officer narrowly missed being hit by the stolen vehicle.
Mr Boon saw a police patrol car stop on Pipiwai Rd and officers setting up road spikes.
"I saw this guy come down with a couple of police cars chasing him. Because of the road spikes, he went off the road through a little drain, round behind an officer, then back on to the road.
"He must have hit the second spike but carried on towards Kamo."
A man who witnessed the arrest said the vehicle being pursued by police was on its rims and "swerving all over the road then crashed into the back of a car at Whau Valley shops".
The witness said it then crashed into a scaffolding truck. The driver of the car already had the door of the moving vehicle open, jumped out and ran off through traffic.
"At that point a policeman pepper sprayed him and a [police] dog caught him on the arm," he said.
Acting Whangarei area commander Inspector Al Symonds said it's alleged the man was seen pulling a woman out of her vehicle at the shopping centre before he drove off.
As police arrived at the scene they spotted the car leaving and a pursuit began, Mr Symonds said.
The man was being treated for dog bites before he was to have been formally interviewed by officers.
