Adam Coulshed, a local construction worker who was on site across the road from the bank, said there was a loud bang followed by plumes of black smoke.
'I thought it was a car accident,' he said.
He said his co-worker helped put out the fire with a shopkeeper from a neighbouring Optus store.
The man was trying to get money from an ATM at the time of the explosion, he said.
'It was just black and there were people with blood [coming out of the bank]