Burns made no attempt to conceal the weapon and members of the public spotted him.
His mother and sister managed to intercept him on Hartstonge Ave and persuaded him to give up the knife.
They could not, however, cool his temper.
By this stage, police had received calls and were looking for Burns, but he made it to the station before they cut him off.
Burns armed himself with a ceramic garden gnome and smashed it on the footpath in front of the building.
Next, he grabbed an Anzac Day commemorative wreath and destroyed that, too, by throwing it against a wall.
His rampage ended when he smashed the station's front window by head-butting it.
When Burns was arrested, he was ''highly agitated'', police said and admitted he was intending to use the knife.
''My life's already ****. I've got nothing to live for,'' he explained.
''I'd much rather die killing a pig than keep on going like this.''
Counsel Rhona Daysh said they were the impulsive acts of a young man fuelled by alcohol.
She described her client as ''bright and sensitive'' and said he had seen the benefits of being free of alcohol while on bail.
Judge Kevin Phillips said there was no obvious remorse exhibited by Burns.
His actions on the day were ''frightening'', the judge said, particularly in light of what happened in Christchurch in March.
''I can fully appreciate the fear you must have engendered in the police constable and the community that saw you walking down the street,'' he said.
Burns was sentenced to 18 months intensive supervision.
Any further animosity towards police, the judge said, would result in the defendant's incarceration.
