NORTH CHARLESTON, S.C. — The police officer who was arrested on Tuesday after shooting and killing an unarmed black man has been fired from the department and the police chief here said Wednesday that he was appalled by what a video of the encounter revealed.

“I have watched the video and I was sickened by what I saw,” Eddie Driggers, the North Charleston police chief, told reporters, at an emotional and often chaotic news conference, with protesters repeatedly shouting and interrupting. “And I have not watched it since.”

Asked whether the proper protocols were followed after the shooting, Chief Driggers said, “Obviously not.”

There were pointed questions about when — and if — first-aid was provided to the victim and if the officer’s version of events was ever in doubt before the video emerged. Officials declined to answer those questions, saying they had immediately turned to the state to carry out an impartial and independent investigation.

“That’s the right thing to do,” Chief Driggers said.

As protesters gathered outside City Hall, the mayor of North Charleston, Keith Summey, made clear that he was trying to calm the community. He said he and the chief had visited the family of Walter L. Scott, 50, the man who was fired at eight times as he ran away from an officer after a traffic stop.

“We let them know how we felt about their loss, and how bad it was,” the mayor said, adding that the city would provide a police escort at the funeral.

Mayor Summey said he had issued an executive order that all of the department’s police officers start wearing body cameras — a tacit acknowledgment of the importance video played in this case.

Mr. Scott’s father, in an interview on the “Today” show on NBC earlier in the day, said he believed that without the video, the officer would never have faced prosecution.

“It would have never come to light. They would have swept it under the rug, like they did with many others,” Walter Scott Sr., the father of the victim, said.

The officer, Michael T. Slager, 33, was being held at the Charleston County Jail after a magistrate judge on Tuesday night denied him bond. Officials said at the news conference that the city would continue to cover health insurance for his wife, who is eight months’ pregnant.