He was wearing a baggy grey hoodie, dark trousers and a beige Halloween-type mask, and was carrying what appeared to be a small dark-coloured firearm.
"At this stage, this is being treated as an isolated incident and officers are focused on catching the man responsible," senior sergeant Vaughn Lapslie said.
Police would like to hear from anyone who may have been in the area at the time as well as anyone who recognises the offender's description, or who has any information about this incident.