The group, from Ladder 113 in Brooklyn, went to the office of state Sen. Zellnor Myrie in the company's fire district in uniform and asked to speak to him, although as a state official he had no involvement in the city mandate from Mayor Bill de Blasio.
"They said they wanted to let people in the community know that the trucks weren't going to be running and that they were going to shut down firehouses," a person familiar with the conversation told ABC News.
It was, the person said, a "cordial conversation" though at one point the firefighters said the "city would have blood on its hands."
The firefighters told the senator's staff member they wanted the choice whether to get vaccinated and expressed a view that it would be safer for them to get tested every week.
Firefighters are one of the lowest groups of vaccinated city workers in New York, though that number crept up during the final day before the deadline, with 77% of FDNY members vaccinated, including 72% of firefighters and 84% of EMS workers, as of Friday night.
About 84% of the New York Police Department is vaccinated, with 1,000 people getting their first doses on Thursday, according to Commissioner Dermot Shea.