Jamie McColl had five stolen guns when he opened fire as sports teams practised on nearby fields of Napier's Park Island.
A section of the city went into lockdown as McColl, 46, stayed close to the car he had earlier stolen.
Stuff reported that in Napier District Court on Friday he pleaded guilty before Judge Russell Collins and entered guilty pleas to charges of burglary, taking a car, discharging a firearm in public and discharging a firearm with reckless disregard.
At 6.30pm on December 10, 2019, he drove the stolen car at speed and performed burnouts on the way.
He came to a stop in the middle of a road in the park where there were members of the public in the park area and sports teams practising.
According to Stuff he got out of the car with five guns and stood in the middle of a road, blocking the way of a man driving a van who had just collected his 13-year-old son from the park.
McColl lifted the shotgun and aimed it directly at the man and his son. The pellets hit the front grill, bonnet and windscreen.
Two girls, aged 13 and 14, were biking along the footpath about five metres from the van.
For the ensuing 90 minutes he paced back and forth near the car in an agitated state.
At one point he said, "today was a good day to die." He picked up one of the rifles, moved it to his shoulder and pointed it towards the nearby rugby club.
He fired the guns three times.
Eventually he put his hands above his head and walked towards a police officer who had been communicating with him.
McColl apologised for his actions, claiming he had not had his medication for three days.
Stuff said McColl had more than 150 previous convictions.
He will be sentenced in December.