Forbes :

A barrage of racial epithets unleashed by former "Seinfeld" star Michael Richards during a stand-up comedy routine drew condemnation from Richards' industry colleagues.

[..]His Laugh Factory tirade began after the two clubgoers shouted at him that he wasn't funny. Richards retorted: "Shut up! Fifty years ago we'd have you upside down with a f------ fork up your a--." He then paced across the stage taunting the men for interrupting his show, peppering his speech with racial slurs and profanities.

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TMZ.com:

Moderating his tone at one point, Richards tells the audience: "It shocks you. It shocks you" and refers to "what lays buried." Read whole article here
With pal Jerry Seinfeld already Letterman's scheduled guest on Monday's "The Late Show," Michael Richards appeared via satellite to apologize for the shocking incident at the Laugh Factory on Friday night. TMZ obtained the horrifying video of Richards in a bigoted tirade against a heckler.

According to a source, Richards was close to tears during the apology.

The Moderate Voice wonders if this isn't the end of Richards' career.