A masked gang left some passengers on an Auckland train frightened while spray-painting a huge "graffiti bomb" on the train's exterior.
An Auckland councillor was among those trapped in the carriage - which filled with fumes from the spray cans being used to graffiti the train.
The train bound for Britomart was hijacked about 4.45pm on Sunday in broad daylight by a gang of around 12 at the Baldwin Ave station.
A spokesman for Auckland Transport said the group hit the train's safety button, which immobilises the train, allowing the vandals enough time to spray-paint it.
The train driver locked the doors shut to keep passengers safe until police arrived.
"That's the safest place for them to be - the last thing we want them to do is go out there," the spokesman said.
Auckland councillor John Watson, a passenger on the train, watched on as the gang raced towards the train in "ninja" masks as it ground to a halt at the station.
"They were sprinting to get to the part of the train that they were assigned, to do."
Distressed passengers were locked in the train as the vandals painted big blocks of colour with their faces wrapped in "ninja" masks.
"Some people were banging on the walls and windows to get out."
For about 10 minutes, the gang raced to spray-paint carriages from top to bottom, as the fumes from the spray cans filled the train carriage.
"The public were imprisoned while they did their stuff, you're like a hostage for 10 minutes," Watson said.
"People inside were getting affected by the fumes, struggling for fresh air."
When the doors finally opened, the gang of men had disappeared - but they had made their mark on the train, signing off their work with "outcasts - till death".
"Older people were getting distressed, and people couldn't see out of the train because the windows and doors were getting graffitied," Watson said.
Footage of the incident was captured on a video posted to social media and the vandals appear to be aged between 18 and 20.
"What it doesn't show is how distressed the passengers were. They were holding the public to ransom, and there was a degree of intimidation to it," Watson said. "It's egotistical voyeurism."
Max Hampton was also onboard the train when the vandals descended.
"The younger people were fascinated by what was happening. But there were a few older people who were obviously not impressed and a couple of people were covering their faces as the fumes were coming in through the air ducts," he said.
It's reported that incidents like this cost Auckland ratepayers as much as $500,000 a year for clean-up and damage costs.
"To me, it's quite a serious thing in this day with examples overseas with people attacking on trains," Watson said.
"It's not an era when people think it's just harmless."
The train was taken out of service immediately after the incident and was sent to the depot in Wiri for the paint to be removed.
Sergeant James Cassin, of the Auckland Police, said it's a "mindless, senseless act of vandalism".
"This appears to be a premeditated and planned attack and we are determined to hold those responsible to account.
"If you have any information that could help our investigation, please contact Auckland City Police on (09) 302 6400."