A 33-year-old was found with gunshot wounds and died on Justin Avenue in Glenroy at 4.30am on March 29.
Officer allege the group all knew each other.
Victoria Police arrested and interviewed both a 18-year-old Campbellfield man and a 48-year-old Thornhill Park man in the months after the incident but they were released “pending further enquiries”.
Yesterday police arrested the 18-year-old in Broadmeadows and charged him with murder.
He had been jailed and is due to appear in court again on August 26.
The 48-year-old was arrested in Thornhill Park on Thursday and has been charged with accessory to murder.
He has been bailed and is due to face court next week.
In April, a 40-year-old man was arrested in Wandong and charged with murder and prohibited person possess firearm.
He is also due to face court on August 26.