He walked through the building and towards the BNZ bank.
About four minutes later, he can be seen jogging along the same service lane out on to Wicksteed St.
Police believe that he walked for some distance before the robbery with his face exposed.
The offender is described as about six feet (1.83m) tall and wearing dark-coloured clothing, possibly a hoodie and blue jeans. He also wore a balaclava over his face and dark-coloured gloves.
At that time of the day there were several people and vehicles in and around this intersection, and police would like to hear from anyone who may have seen the man in the area around the described route, Mr Buchanan said.
Also of interest was any information on vehicles in the area of the Wicksteed St side of the service lane, which may have been either waiting for, or picking up, the man.
"It is vital that this man is caught quickly and information from the public will help police to achieve this," Mr Buchanan said.
Contact Detective Andrew Buchanan of Whanganui Police on (06) 3490682 or ring anonymously to Crimestoppers on 0800 555 111.
