A critically injured Mr Radulovic was found on Donnelly Street in Balmain following reports of an assault on July 29.
He was taken to hospital but died shortly after.
Wests Tigers NRL hopeful Masei Tavui, 19, was charged with Mr Radulovic's murder after tactical response police raided a property in Austral, west of Liverpool, on Tuesday.
He was refused bail and ordered to return to Downing Centre Local Court on December 12.
Following further inquiries, police say a 21-year-old man was arrested over the killing by strike force detectives at Liverpool on Wednesday.
He has also been charged with murder and failing to comply with an evidence access order.
Remanded in custody, the man will appear before Liverpool Local Court on Thursday.
Police were told Mr Radulovic was injured during a fight with two men, who fled in a white Jeep.
The Jeep was found burnt out in nearby Five Dock with a firearm inside.
Tavui is yet to debut for the Tigers' NRL side but has played as a forward for affiliate club Western Suburbs Magpies in the SG Ball under-19s competition this season.
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