When armed robbers demanded Abdul Hakim Naurozi hand over the drugs he was delivering them, he refused and asked if they were going to shoot him.
"I'll shoot you," Blake Wynne replied.
Wynne was armed with a shotgun as he got into the car behind 31-year-old Mr Naurozi.
His friend, Jordan Fiscalini, stood beside the front passenger door armed with a knife, blocking their victim's exit.
Wynne and Fiscalini had been involved in an armed robbery in South Melbourne earlier that day, using the gun that Fiscalini had stolen from a friend.
After that robbery they drove to Wynne's partner's home and arranged to buy drugs and came up with the plan to rob Mr Naurozi of the GHB and money when he arrived.
"Give me the juice," Wynne had demanded, in reference to the GHB.
When Mr Naurozi refused, Wynne struck him across the back of the head with the gun.
His finger was on the trigger as he hit his victim and the gun went off, shooting Mr Naurozi in the left side of the face.
Wynne and Fiscalini fled, but not before stealing vials of drugs.
Fiscalini drove away and, after ditching the gun near a playground, Wynne hid in a park until he was discovered by the police canine unit.
Wynne was 22 at the time of the killing in Endeavour Hills in May 2020. He had been released from custody just six days earlier.
He has pleaded guilty to murder. Both he and Fiscalini, who was then 19, also pleaded guilty to charges of armed robbery, attempt to commit armed robbery and being prohibited persons in possession of a firearm.
Janan Naurozi said her family had been devastated by the loss of her eldest son, which happened just a year before she lost another son in an accident.
She described him as an intelligent and charming boy.
He had been the man of the house when they lived in a refugee camp before coming to Australia and had helped her with the family's finances.
They now face losing their home after falling behind on rent and bills.
Theo Alexander, representing Wynne, said he had a tough upbringing and was diagnosed with antisocial personality disorder and substance abuse disorder.
Fiscalini's lawyer Andrew Jackson said his client had an IQ of 60, putting him in the bottom one percentile.
"If there was any difficulty that could be encountered, I would suspect Mr Fiscalini has encountered it growing up," he told the Supreme Court.
Justice Christopher Beale will sentence both men at a later date.
