News anchor's off-air meltdown leaked online

A US news anchor has had his off-air temper tantrum leaked online in a humiliating moment.

MSNBC host Lawrence O'Donnell went into a full-blown, profanity-laced meltdown over a mysterious hammering noise in the background of his broadcast.

Initially, Lawrence was upset that he couldn't hear audio in his earpiece.

"Someone in that control room is out of control," he said. "F***. Goddamnit."

And that was just the start.

"Every time we go to a [clip], there’s a woman talking in my ear about something that has nothing to do with what we’re doing here," he complains at one point.

But O'Donnell finally loses control over a hammering sound that can be heard in the background of the video.

"STOP THE HAMMERING!" he screams. "STOP THE HAMMERING OUT THERE! WHO’S GOT A HAMMER? WHERE IS IT? WHERE’S THE HAMMER?"

"I’LL GO DOWN TO THE GODDAMNED FLOOR MYSELF AND STOP IT," O'Donnell vows. "KEEP THE GODDAMNED COMMERCIAL BREAK GOING!

"CALL F***ING [MSNBC President] PHIL GRIFFIN! I DON’T CARE WHO THE F*** YOU HAVE TO CALL!" he adds. "STOP THE HAMMERING. EMPTY OUT THE GODDAMNED CONTROL ROOM AND FIND OUT WHERE THIS IS GOING ON!"

Eventually, after a stressed-seeming producer assists him, Lawrence seems to calm down a little.

"I told you why I wanted those f***ing words cut," he says to an unknown producer before adding.

"It just f***ing sucks. It f***ing sucks to be out here with this out of control shit."

Within minutes of the footage emerging online, Lawrence had tweeted an apology.

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