As he was walking away, he threatened to "blow up" the security officer and other Winz staff, the court heard.
He then pulled a loaded .22 sawn rifle out from down his trousers and let a shot off into the air.
Moulton, or Aranui, continued yelling and shouting expletives before driving off at speed.
He dumped his car in nearby Bass St before being chased by armed police who soon caught up with him.
They later found the gun in his car along with some ammunition and 4g of cannabis.
Moulton appeared in the dock at Christchurch District Court today with a shaved head showing off skull tattoos.
He earlier pleaded guilty to threatening to kill, possessing a firearm and discharging it in public, driving while disqualified and possessing cannabis.
Defence counsel Donald Matthews said Moulton had taken part in a restorative justice conference with two Winz victims, and a regional manager.
Mr Moulton, who has a history of drug and violence offending, offered his apologies to them.
Later, he told his lawyer that "fronting up" to his victims had been the hardest thing he'd ever done.
Mr Matthews said Moulton had gone to Winz seeking help that day, and the upshot is that he is finally getting the help he needs behind bars.
In jailing Moulton to two years and eight months, Judge Paul Kellar said the premeditated offending had had a "pretty significant effect" on the security officer.