This post has been updated.

The American Civil Liberties Union chapter in Missouri is demanding that the state’s highway patrol identify and remove a law enforcement officer who was videotaped telling a protester in Ferguson, Mo., “I will fucking kill you” Tuesday night.

“We are confident that you will agree that law enforcement officers who are unable to maintain a professional demeanor and exercise appropriate restraint should not be involved,” the organization wrote in a letter to Missouri Highway Patrol superintendent Ron Replogle.

The ACLU cited a YouTube clip of a longer video taken from the streets in Ferguson posted by a user tagged as Rebelutionary_Z. As protesters move toward some commotion, they are approached by a uniformed officer with his firearm raised.

“I will fucking kill you,” the officer says. “Get back.”

“You’re going to kill him?” the videographer asks. “What’s your name, sir?”

“Go fuck yourself,” the officer says. He is soon guided away from the confrontation by another uniformed officer.

The identity and jurisdiction of the officer are not immediately clear from the video. The ACLU said it believed it was “a municipal police officer.”

Image via UStream.

UPDATE: 5:45 p.m. ET

The ACLU tweeted Wednesday afternoon that the officer in the video had been removed from duty.