A video on the site shows the actor, 57, who made a name for himself as Kramer, Jerry Seinfeld's neighbor on the sitcom "Seinfeld," repeatedly yelling racial remarks at a man who sat in the audience at the comedy club. It apparently happened after someone in the crowd said he wasn't funny.
"Fifty years ago we'd have you upside down with a f------ fork up your ass," he says while on stage.
"You can talk, you can talk, you're brave now motherf------. Throw his ass out. He's a n-----! He's a n-----! He's a n-----! A n-----, look, there's a n-----!"
Gasps and boos from the crowd can be heard in the video. One of the men who Richards yelled at shouted back "That's un-f------ called for. Ain't necessary," TMZ reports.
A call from the The ShowBuzz to the actor's agent was not returned on Monday morning.
Darryl Pitts is a black man who was in the audience that night. "He just took all of the air out of the room," Pitts told CNN. "He needs to make a public apology to everyone."
2CNN reports that Richards was back on stage 24 hours later. He told CNN off camera that he felt sorry for what happened and he made amends — to whom or how, he didn't say.
Jerry Seinfeld issued a statement to the Associate Press on Monday saying he was "sick over this."
"I'm sure Michael is also sick over this horrible, horrible mistake. It is so extremely offensive. I feel terrible for all the people who have been hurt," Seinfeld said.
Comedian Paul Rodriguez was at the club when it happened and told the AP he thought Richards' comments crossed the line.
"Once the word comes out of your mouth and you don't happen to be African-American, then you have a whole lot of explaining," he said. "Freedom of speech has its limitations and I think Michael Richards found those limitations."
According to the AP, actor-comedian George Lopez told Los Angeles TV station KTLA that he thought Richards' lack of stand-up experience may have been a factor.
"The question is you have an actor who is trying to be a comedian who doesn't know what to do when an audience is disruptive," Lopez said. "He's an actor whose show has been off the air, he shouldn't ever be on a stand-up gig."