A Los Angeles City Fire Department captain who railed against the city, the department and his own union leaders over an imminent vaccine mandate for all city workers is under an internal investigation.

"I am so hopping mad right now, you have no idea. My head could pop," Capt. Cristian Granucci told viewers as he launched into a 12-minute video rant on Monday in which he threatened to sue the local firefighters union and the city.

Granucci, who says he's a 31-year veteran, gnashed his teeth as he called the COVID-19 vaccine mandate "total tyranny" and insisted that he is "done being silent on this matter, and so are many of our members."

The mandate goes into effect in early October

The city's recently passed rule is awaiting signature by LA Mayor Eric Garcetti and won't go into effect until early October. At that point, all city employees will have to show they've received the COVID-19 vaccine or submit to twice-weekly testing. Refusing both of those requirements would lead to termination.

Wearing an LAFD hat and LA City Fire Department T-shirt, in what appears to be a fire station, Granucci acknowledged he will likely "catch total grief" for stating his opinions then proceeded to accuse union officials of sitting on their hands as the "mandate came to Los Angeles." He also complained that union leaders abandoned their responsibilities "to protect the little guy," opting instead "to play politics with this."

The purpose of the video, he said, was to offer a warning of the act-now-or-else variety.

"I am putting my administration and my union on blast," Granucci said, pointing a finger into the camera.

"There is a large group of us, in the hundreds, and we have an attorney on retainer and he is a shark."

Granucci alludes to a vaccine divide. Nearly half of LAFD firefighters are not vaccinated

As of Tuesday, it appears the original video has been taken down, but a reposted version of Granucci's monologue has been seen more than 64,000 times.

LAFD spokeswoman Cheryl Getuiza confirmed that the department became aware of the video on Monday. It has since launched an internal personnel investigation into the captain, and she said he may face disciplinary action.

"While we respect the individual's right to his opinion, he is not authorized to speak on behalf of the Department," Getuiza said by email. "The individual is in uniform and appears to be on duty, thereby giving the impression that he is speaking in an official capacity."

Getuiza said that there is no timeline set for the investigation but that it will include interviews and consultation with the City Attorney's office.

President of the firefighters Local 112 union, Freddy Escobar said the issue over mandatory vaccinations has sparked "passionate discussion" within the city's fire stations. And, while officials encourage members to get the shots, "we do not support any City policies that make it a condition of employment," he said.

"The majority of our firefighters have voluntarily been vaccinated and more are choosing to do so each week," Escobar said in an emailed statement.

LAFD could face a staffing crisis if the firefighters refuse to comply

The latest LAFD data show that 54.26% of sworn members are fully vaccinated and that 61.6% have received at least their first dose.

Since the rollout of the vaccines, the department has played an integral role in the city's inoculation campaign, including at events where firefighters deliver the jabs. It is unclear whether those administering the shots are required to be vaccinated.

Escobar noted another problem currently facing the department: understaffing and retention, which would be exacerbated if nearly half of the LAFD were to be fired for failing to comply with the vaccine mandate.

"We are in discussions with the City because our highly skilled and experienced LAFD Firefighters and Paramedics cannot be easily replaced — especially in a department that is already understaffed," he said. "The unexpected departure of even a small percentage of our workforce would have a devastating impact on public safety in Los Angeles."

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