Wellington police are on the hunt for men who allegedly ran up to a train on the tracks, apparently to start tagging it.
On December 19, say police, the men ran up to the passenger train in Upper Hutt, while it was stationary. They then caused "extensive damage" to the train.
The police have now taken to Facebook to appeal for help identifying the men, who were photographed in the act by outraged passengers.
The police spokesperson said the men's actions were not only illegal, but also "highly dangerous".
Many locals have commented on the post, noting their surprise at the mens' ages.
"Here I was thinking it was teenagers that did that sort of thing," commented Courtney Chalmers.
"What a couple of losers. Pathetic childish behaviour," Stephanie Tidman said.
Other locals commented on the spraypaint the men had in their hands, saying it looked like a brand that was only sold at Pete's Emporium.
A police spokesperson said the public appeal had turned up "several strong leads" which they were now following up.
He said being on train tracks was illegal, and wilful damage was also an offence.
But the incident could easily have been even worse.
"It's a live train that stopped briefly to let passengers on and off. It could quite have easily turned into a situation where one of them are caught on a train part and potentially dragged by the train.
"The train driver may not know they are there, so wouldn't know it's not safe to move forward.
"Also the delays and disruptions this causes because they would likely need to remove the train from service for repairs."