Caught on video --  a Queens man being tasered by an NYPD plainclothes sergeant after the two get into a profanity laced argument.    

The altercation began when Sean Marcellin, 24. was stopped as he drove in Far Rockaway over the weekend. Police say Marcellin failed to signal; he says he did.  

As the dispute turned heated, a bystander used his cellphone to livestream it on Facebook.

"You said you are going to break my jaw!' the sergeant says.

"No, no! You just said you are going to tase me!" the driver replies.

At one point, the bystander tells the officer he's gone too far, saying, "You got to remain professional at all times."

"I am professional. I asked him for his license six times. He's been refusing since then. He is now going to get locked up or get a summons depending on my mood, simple as that," the sergeant replies.

Police say that when Marcellin threatened to find out where the sergeant lives and beat up his kids, uniformed officers pulled him from the car. The video shows the sergeant then confronted Marcellin and tased him, even though the driver was being held by other officers. 

NY1 showed the video to Brooklyn College Professor Alex Vitale, who teaches policing and sociology. 

"His arms are behind his back and then they taser him. I mean his arms are behind his back," Vitale said.

"Instead of stepping back and figuring out what is going on, the police go right into more use of force, more confrontation,  inappropriate language that just made the situation more combustible."

After Eric Garner's police chokehold death, the NYPD trained cops in de-escalating confrontations. Professor Vitale says that did not happen here.

"Every day police have to put up with people that give them a hard time. And the question is, 'Are they going to react to that through escalation, heightened levels of use of force, putting people's lives in danger? Or are they going to try to work those things out?'"

The NYPD Patrol Guide tells police to consider several factors in whether to use a taser... including the nature and severity of the crime ... and the "immediacy of the perceived threat or harm."

Charges against Marcellin include making a terroristic threat against an officer and driving without a license. He was released without bail and is due in court next month. The Legal Aid Society says the case is bogus and should be dismissed.