A man and three women were in a carpark of a licensed premise in Talmage Street about 1am on Tuesday, December 19 when a man walked out from behind a dumpster.
He pointed a firearm at the group and made demands for the building to be opened.
He struck the male victim, aged in his 70s, in the chest, arm and head with the firearm and continued to make threats against the group, pointing the firearm at one of the women, also aged in her 70s.
The man ran from the scene, towards Albion Railway Station, after he picked up a set of keys dropped by the male victim, which activated the alarm on a car.
The male victim suffered a serious head injury and an arm injury. The three female victims were physically uninjured.
The offender is described as being about 182cm tall, with a thin build, light coloured eyes and perceived to be Caucasian in appearance.
At the time he was wearing dark, loose-fitting pants, a dark windcheater, runners and a dark-coloured balaclava over his face.
A reward of up to $350,000 will be paid, at the discretion of the Chief Commissioner of Police, for information leading to the apprehension and subsequent conviction of the person or persons responsible for the assault of the man.
Police are keen to speak to anyone who was in the area on Tuesday, December 19 following an event at the premises on Talmage Street.
Anyone with information should contact Crime Stoppers on 1800 333 000.
