Abdullah Bahsa was shot and killed in a targeted attack in Lidcombe, in Sydney's west, on March 16.
Seven men have been charged in connection with the incident, but police are not satisfied and made a public appeal in search of more alleged offenders.
Authorities are chasing a man described as being of Pacific Islander appearance, aged in his late teens or early 20s, 190cm tall, and of slim build. He also may have a moustache and unshaven face.
In CCTV footage released by authorities, he is seen wearing a black hoodie with a prominent yellow Nike logo, black track pants, and white sneakers.
Through tears, Mr Bahsa's sister, Manal, made a direct appeal to the individual being sought by authorities.
"I'd ask you to consult your own conscience. Imagine this was your family member, and you're sitting here today appealing to them," she said.
"You know who you are, you know what you've done."
Ms Bahsa pleaded with the public to come forward with any nuggets of information.
"No matter how insignificant this information might seem to you, it might be just the piece of information that we need to to give Abdullah justice and to put an end and closure to our suffering."
Auburn Police Area Acting Commander Darren Sly urged the man to turn himself in before police come looking for him.
Ms Bahsa described her brother as a very kind and generous man who also acted as a carer for their elderly mother.
"He had a family who loved him. He was a brother to me and a son to my mother, and we miss him very, very much," she said.
"His murder has left a very big gap in our lives."
Police are asking anyone with information to contact Crime Stoppers.
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