The victim suffered a long cut "from between his eyebrows to the base of his nose", Mr Poland said.
He was lucky not to have been struck in the eye, as he could have lost his sight, Mr Poland said.
The brutal attack didn't deter other workers and customers at Sylvia Park mall, who continued to chase the alleged thief and hold him down until police arrived and arrested him.
Mr Poland said it was "a good effort by the members of the public to catch this guy".
The injured Vodafone worker was taken to the East Tamaki Healthcare clinic in the mall, where his partner arrived to support him.
He required "36-odd stitches" to his face and was "distressed" by the incident, but was not admitted to hospital.
The man was recovering at home and having trouble remembering details of the incident or what the alleged offender looked like.
Despite his actions, the man did not consider himself a hero, Mr Poland said. "He's a pretty humble guy, he just saw the ladies in distress and didn't know what was going on, heard the smashing of the glass and just acted.
"I guess he just did what he thought was best at the time and went to these ladies' aid."
Walker and Hall sales assistant Sam Bhutani described how he saw the man smashing the counter at the Michael Hill store as he prepared to open his store.
"I put down my coffee and I ran after him, and at the same time the Vodafone guy who got hurt, he ran with me.
"We tried to jump on him, but [the Vodafone worker] got there first and [the alleged thief] smashed the hammer on him.
The alleged thief then started running outside the mall near the Starbucks. "And then we started screaming and stuff, and the people at the Starbucks - one guy, probably a customer, he got him."
The customer tripped the fleeing man with his legs, and held him down.
Mr Bhutani said the hammer attack victim was "bleeding very bad".
It was the second time the store had been robbed this month.
Police want to speak to anyone who witnessed the latest incident. A 22-year-old man is to appear in Auckland District Court today charged with aggravated wounding and shoplifting.
- additional reporting, Eli Orzessek and Susan Strongman