'NBC Nightly News' interrupted by fire alarm; Brian Williams doesn't miss a beat

Brian Williams led off Tuesday's (Nov. 29) "NBC Nightly News" with a story about the American Airlines bankruptcy -- and a little bit of unplanned accompaniment in the background.

A few seconds into the broadcast, a fire alarm started droning in the background. Williams looked toward the ceiling and let viewers know what was happening, then coolly continued with his introduction.

The alarm continued too, and before Williams threw the story to correspondent Tom Costello, he noted that no one was in any danger and the alarm was just a drill. And we all learned the "Nightly News" studio isn't soundproof.

Here's video of the badly timed alarm, courtesy of Mediaite.