It looks like NBC is so rattled by Charles Gibson's second week on top in the evening news race that heads are starting to roll: Radar hears that Nightly News With Brian Williams executive producer John Reiss, who got a very public dressing down from the affable anchor in the NBC newsroom earlier this month, has been shown the door.

Sources say an official announcement will be delayed for several weeks to avoid the appearance of NBC panicking at losing ground in the ratings race. Reiss and an NBC News spokeswoman did not return repeated calls for comment.

NBC has had a lock on the evening news for years, but the stranglehold has started to loosen of late: Last week Gibson beat Williams by more than 300,000 viewers, reprising a victory he scored two weeks prior. But one TV news insider says it's not just the ratings that spelled the end for Reiss.

He was not a favorite of NBC Universal honcho Jeff Zucker, who ascended to the top slot at the company earlier this month. "The instant Zucker got that job," says the source, "Reiss was toast."

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