The robber started chasing the staff member who hid behind the locked door, while the other man began clearing the cigarettes from the display cabinet behind the counter.
Prema looked at the CCTV footage later and said the robber swung the machete several times and also smashed the store telephone. He had also smashed a hole in the backdoor.
"I'm just grateful my staff wasn't behind the counter because he did want to injure - the way I look at it.
"We are just lucky he wasn't behind the counter because there is only one way from the counter to run out and they would have confronted him."
Prema's wife, who was upstairs with their young grandchildren, looked at the surveillance footage playing in their house and saw the man with the machete pacing the store while the other man took between $1500 and $2000 worth of cigarettes. She immediately called the police.
The men, dressed in hoodies and aged between 25 and 30, also stole some chocolate bars, Prema said.
They were only in the store for about 40 seconds and fled before police arrived.
Prema, who has operated the shop for 30 years, said it was very scary and could have been much worse.
About 15 minutes earlier his wife had been in the shop with his grandchildren, aged 3 and 4, and he dreaded to think what would have happened if the robbers had entered while they were still playing in the store.
"They had literally just swapped places. If my grandchildren were there I don't know how much they would have got hurt.
"This thing this morning has really scared me. Like I say if it was a matter of 10 to 15 minutes the kids would have been there, she would have been behind the counter. I don't know what would have happened with someone running with a machete and my grandkids would have definitely got frightened.
"It was all a bit frightening. Very very frightening in fact. When I think of it too - I think what should we do, get rid of the store?," he said.
"Being 10.30am and Williamson Ave - you don't expect people to come into this are doing such things."
A police spokeswoman said police were still investigating and looking for the thieves who fled in a vehicle. Police also had CCTV footage.