Police are now searching for the attacker, and have called on witnesses to contact Crime Stoppers on 1800 333 000.
The attack comes as coronavirus panic shopping has escalated in recent days, with unbelievable and sometimes violent scenes unfolding in supermarkets around the country.
A witness told Radio 3AW that three police cars and two ambulances rushed to the scene, and the supermarket was taped off by police. 'We saw everyone running in there. It is quite scary,' the witness said.