The 18-year-old, who authorities said was out on bail for "serious matters" at the time, handed himself in to Northern Territory police on Thursday morning and was subsequently charged with murder.
The incident triggered a quick reaction from politicians, with the NT parliament to reconvene on Wednesday to pass legislation ensuring fewer people were released on bail.
Chief Minister Lia Finocchiaro said she wanted the NT to have the country's toughest bail laws following the killing of 71-year-old Darwin store owner Linford Feick.
"We're making sure we are taking strong action right now … and with these changes, we should see less people bailed," she said.
"If you do the wrong thing, we'll find a bed for you in a prison."
The legislation will be modelled on Victorian and NSW laws, under which a judge must be satisfied that an offender is not going to pose a risk to the community if granted bail.
The Darwin community has been left reeling since Wednesday after Mr Frick was stabbed at his Nightcliff Friendly Grocer store at about 5.15pm.
He accused the teenager of theft before the 18-year-old allegedly attacked him and fled the scene on a bike.
The death comes after Darwin bottle shop worker Declan Laverty was fatally stabbed in 2023 by a man on bail, an incident that also ushered in stricter legislation.
Under the so-called Declan's Law, electronic monitoring devices became mandatory for repeat offenders granted bail and the scope of offences triggering a presumption against bail was expanded.
"Territorians are angry, sad, they are frustrated and they are asking themselves when will enough be enough," Ms Finocchiaro said.
The union representing retail staff said more had to be done to protect workers in the NT.
"Nobody should go to work and not come home," the Shop, Distributive and Allied Employees' Association's Josh Peak told AAP.
"Two violent deaths in the retail sector in the Northern Territory in the last two years shows that more must be done to keep workers safe."
The NT's prison population has reportedly risen by more than 500 people since the Country Liberal Party won the 2024 election with a tough-on-crime agenda.
Meanwhile, floral tributes have been laid outside the Nightcliff shop, with an outpouring of grief on social media.
Mr Feick's wife Margaret described her husband as "a beautiful man, a true gentleman and my soulmate".
"I am sitting here at 3am too broken to go to sleep because my life has been shattered," she wrote on Facebook.
"My beautiful husband of 51 years was stolen from me, his children and his seven grandchildren."
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