Good thing Brian Williams has experience as a firefighter.

As the NBC “Nightly News” anchor opened Tuesday’s newscast with a segment about American Airlines’ bankruptcy, the fire alarm in the studio went off.

How did the newsman—who was once a volunteer firefighter and helped snuff out a blaze in Manhattan three years ago—react to the alarm?

First, he tossed it over to NBC’s Washington, D.C., bureau, but when that segment was over the fire alarm was still moaning—and it continued through most of the program.

“Williams kept his cool, offered an easy chuckle and assured viewers that it was just an alarm and there was no danger,” writes Al Tompkins on Poynter.org. “Surely the problem would go away. It didn’t.”

The blaring alarm—complete with a recorded announcement—quickly became a hot topic in social media. On Twitter, Williams received accolades for “redefining professionalism.”

Meanwhile, Erika Masonhall, the director of PR for NBC News who handles PR for "Nightly News," fired off a series of tweets during the live broadcast—tweets that were informative and light-hearted.

“Don't be alarmed - it was only a test! Fire alarm went off in @nbcnightlynews studio. Live TV, folks.”

“On the bright side: @bwilliams is a pro with a good sense of humor …”

“This is the first fire alarm in our new @nbcnightlynews studio. System should have been shut off -- but clearly still working out the kinks.”

“DC/west coast, you'll miss the excitement -- we're fire-alarm-free for a new live feed of @nbcnightlynews #fingerscrossed”

NBC reshot the program for its West Coast viewers.