NEW YORK (NewsNation Now) —New York City firefighters held a massive protest Thursday outside the home of Mayor Bill De Blasio.

“We are citizens of the United States of the America,” one protester shouted.

Another protester said, “These men and women who took that oath to the citizens of New York, they want to come to work next week.”

They are angry about the city’s vaccine mandate. Police officers, firefighters and most other city workers must show proof they’ve gotten at least one dose of the COVID-19 vaccine by 5 p.m. Friday or they will be placed on unpaid leave starting Monday.

Union leaders including Firefighter Association President Andrew Ansbro are telling unvaccinated members to report for duty and let the city send them home.

“It’s an artificial deadline created by the mayor,” Ansbro said. “There’s no reason why there isn’t more time for this.”

Blasio has been firm on the current deadline. On Wednesday, the Police Benevolent Association, which represents about 24,000 police officers in the New York Police Department, filed a lawsuit with the city over the mandate. The judge refused to pause the mandate and sided with the city.

“We’ve given incentives, we’ve given time, we’ve given voluntary opportunities — now we need this,” Blasio said during a news conference.

About 68% of the city firefighters are vaccinated, according to NYFD. The department, whose EMTs and paramedics were working around the clock in the early days of the pandemic, lost 16 workers to the virus.

Members of the department are concerned that fire departments could shut down and service capacity could drop by 20%, leading to a dangerously high increase in emergency response times. Some firefighters grimly predict that people could die.

“We’ve sent messages to the mayor, we’ve sent messages to the administration, said James McCarthy, president of the FDNY-Uniformed Fire Officers Association. “They’ve ignored those messages.”

It’s not just firefighters. An estimated 6,000 members of the NYPD are also unvaccinated, which the police commissioner says could lead to a serious problem fighting crime starting next week.

City teachers have already been put under a mandate, and the state has done so for health care workers. But most city workers have been able to get COVID-19 tests weekly to avoid being vaccinated.