The gunman was found dead after a police shootout, during which an officer was shot and injured. Four civilians were also injured.
The shooting happened near hotels where Team Norway and other soccer teams have been staying.
New Zealand Prime Minster Chris Hipkins said the tournament would go ahead as scheduled.
“Clearly with the FIFA World Cup kicking off this evening, there are a lot of eyes on Auckland,” Hipkins said. “The government has spoken to FIFA organisers this morning and the tournament will proceed as planned.”
“I want to reiterate that there is no wider national security threat. This appears to be the action of one individual.”
Hipkins said the shooter was armed with a pump-action shotgun. Police arrived within minutes of the first emergency call and ran into harm’s way to save lives, he said.
“These kinds of situations move fast and the actions of those who risk their lives to save others are nothing short of heroic,” Hipkins said.
Police Commissioner Andrew Coster said the gunman was a 24-year-old who had previously worked at the building site, and the motivation for the shooting appeared connected to his work there.
The gunman had a history of family violence and was serving a sentence of home detention but had an exemption to work at the lower Queen Street site, Coster said.
The gunman began shooting at about 7:20 am. and police soon swarmed the area.
He moved through the building firing at people, Coster said, as many workers fled or hid. The gunman then barricaded himself in an elevator shaft on the third floor, Coster said, where SWAT-type officers engaged him after securing the floors above and below.
“The offender fired at police, injuring an officer,” Coster said. “Shots were exchanged and the offender was later found deceased.”
Coster said it wasn’t yet clear if police had shot the gunman or he had killed himself. He said the shooter didn’t have a gun license and so shouldn’t have been in possession of a weapon.
Outside, armed police officers had the commercial business district on heavy lockdown with streets cordoned off surrounding the tourist harbour ferry terminal area. Police demanded bystanders disperse and ordered people inside their office buildings to shelter in place.
The incident comes as soccer teams and fans gathered in New Zealand for the FIFA Women’s World Cup. The opening match is scheduled for Thursday between New Zealand and Norway. Hipkins said he was reviewing whether he’d attend the match as planned.
Team Norway captain Maren Mjelde said teammates woke up quickly when a helicopter began hovering outside the hotel window.
“We felt safe the whole time,” she said in a statement. “FIFA has a good security system at the hotel, and we have our own security officer in the squad. Everyone seems calm and we are preparing as normal for the game tonight.”
Team USA said all its players and staff were accounted for and safe. It said the team was in communication with local authorities and proceeding with its daily schedule.
New Zealand banned assault weapons in 2019, weeks after a gunman slaughtered 51 people at two mosques in the city of Christchurch during the nation’s worst mass shooting.
A subsequent buyback scheme saw gun owners hand over more than 50,000 AR-15-style rifles and other assault weapons to police.
The ban does not include all semi-automatic weapons. Coster said the gunman’s shotgun is not on the list of banned weapons.
“I want to acknowledge that this has been a shocking and traumatic event for those people who came to work and found themselves in the middle of an armed emergency,” Coster said. “Thankfully, many people were able to escape the building, but I know for those who hid or remained trapped, this was a terrifying experience.”
Coster said the officer who was shot was taken to a nearby hospital in critical condition, had stabilized, and was expected to undergo surgery Thursday. He said the others had injuries ranging from moderate to critical. It wasn’t immediately clear if all those injured had been shot.
Officials at Eden Park, where the opening match is taking place, said they were encouraging ticket holders to arrive early and there would be an increased security presence at the venue.
Tourism New Zealand cancelled a media welcome party that was to have been held Thursday afternoon at a location within the cordoned-off area.