"I was walking down to my store, just diagonally opposite to Michael Hill... and I saw the guy smash the counter," he said.
"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 he [the Vodafone worker] got there first and he [the shoplifter] smashed the hammer on him.
"I fell down, and then another guy came out from somewhere. And then he [the shoplifter] 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 man managed to trip the fleeing thief with his legs, and hold him down.
Mr Bhutani then took the hammer from the man's hands, and mall security was called.
The injured Vodafone worker was taken to the East Tamaki Healthcare clinic in the mall.
The man required "dozens" of stitches to his face, police said, but he was not admitted to hospital.
He is understood to be "distressed" by what happened.
Mr Bhutani said he would try to contact the man to see how he was.
"I hope he's fine ... he was bleeding very bad."
The sales assistant joked the incident was a "morning cardio" for the up to six people who chased down the suspected thief, but said it was "pretty scary" for the workers and shoppers going about their business in the mall.
It was the second time Michael Hill had been robbed this month, Mr Bhutani said.
"The last time the counter got smashed, it broke one of the windows of our store.
"But thank God, it's been twice and our jewellery store is not the one."
A spokeswoman for Vodafone confirmed a team member from its Sylvia Park store was injured during the incident.
"Since the incident this morning, our focus has been on our team member's wellbeing," she said.
"We have been in touch with him and he is now at home resting.
"The team here at Vodafone will continue to support him through his recovery."
Detective Sergeant Nick Poland from the Auckland City Crime Squad said that had it not been for the Good Samaritan's intervention, the alleged offender could have fled with nearly $40,000 of jewellery.
"After he was hit, the injured man desisted and others took over the chase resulting in up to six people detaining the accused until Police arrived a few minutes later."
Detective Sergeant Poland said the shop owner and staff are very thankful to all those who helped arrest the alleged offender.
He said it's "very unfortunate" that the first man to come to the aid of the robbery victims was so severely injured.
Victim Support has been called in to assist the injured man and his family, who Police say are understandably distressed by the morning's events.
Police have praised the actions of those who helped out.
They would like to speak to anyone who left before Police had a chance to get their names and contact details.
These people are encouraged to contact Detective Constable Alex Lawton on 09 302 6557.
