Unfortunately the jewellery store had been robbed a couple of times before, he said.
Now the witness wants to be careful how the incident is portrayed in case it encourages others.
"The hard thing is you don't want to glorify stuff like this. The guys have been caught, the girls in Michael Hill were put in an awful position that's horrible to go through.
"Otherwise we'll get other idiots going out there to do the same thing."
He said the store's employees were left shaken by the incident.
"It's not the sort of thing you often get, two guys wielding hammers and things... It would shake anybody really."
He said the public were very helpful in getting the licence plate number and procuring surveillance footage. The ANZ bank across the road saw what was happening and called the police to say there was a robbery in progress and police were quick to respond.
Michael Hill Jeweller declined to comment.
Three men aged 22, 23 and 24 were arrested. They will face several charges and are expected to appear in North Shore District Court today.
Police have also recovered the stolen jewellery.
Detective Sergeant Steve Brewer said excellent work was done by police and the public.
"We really appreciate all our community on the North Shore and across New Zealand does to help keep our community safe.
"This was a great outcome and I hope the quick arrests will provide the victims with some degree of comfort."
