"It was only when the firefighter explained he was responding to a fire call that he was allowed to continue, but the male then followed him to the Russell Fire Station, where fellow officers intervened."
Police say the man left the area a short time later, having threatened that he would return with a friend.
"Witnesses have been spoken to and positive enquiries are continuing to locate the male involved," the police spokeswoman said.
"Police are confident of a swift and successful resolution to this matter."
It is not the only recent incident in which a firefighter has copped abuse on the job.
At the start of December last year, two firefighters suffered bloody noses while trying to break up a brawl at a crash at Waihi Beach. A 17-year-old was arrested over the matter.
Last year more than 2300 abusive altercations, including assault, were reported by ambulance officers by mid-December.
Meanwhile, police officers reported 346 assaults in 2017 and reported more than 200 assaults by September last year.