Matt Lauer has been fired by NBC over an allegation of "inappropriate sexual behavior," the network announced Wednesday morning at the start of the Today show he had hosted for more than two decades.

"We just learned this moments ago, just this morning. As you can imagine we are devastated and still processing all this," Today co-host Savannah Guthrie, holding back tears, said as the show opened.

"I'm sure we will be learning more details in the days and hours that come, and we promise we will share that with you," Guthrie said. "For the moment, all we can say is we are heartbroken. I'm heartbroken for Matt. He's my dear, dear friend and my partner, and he is beloved by many, many people here."

She said she also was "heartbroken" for the "brave colleague" who reported Lauer.

NBC News Chairman Andrew Lack sent a memo to employees informing them of Lauer's termination, noting the Today show host was fired following a serious review of a "detailed complaint from a colleague about inappropriate sexual behavior in the workplace."

The complaint was the first its kind against Lauer, Lack told employees, but the network had reason to believe it wasn't an "isolated incident."

Ari Wilkenfeld, who told the New York Times he is the lawyer for the unnamed woman accusing Lauer of misconduct, said the pair met with representatives from NBC's human resources and legal departments Monday night.

"Our impression at this point is that NBC acted quickly, as all companies should, when confronted with credible allegations of sexual misconduct in the workplace," Wilkenfeld said in a statement. "While I am encouraged by NBC's response to date, I am in awe of the courage my client showed to be the first to raise a complaint and to do so without making any demands other than the company do the right thing."

Both NPR's David Folkenflik and Page Six's Emily Smith reported that Lauer's behavior involved an alleged incident at the 2014 Winter Olympics in Sochi, where he acted as NBC's primary host after Bob Costas developed an eye infection. Folkenflik added that Lauer's accuser faced a "significant power differential" with the Today show host.

Lauer has not yet commented publicly about his firing.

The news comes less than two weeks after  CBS fired Charlie Rose, its own morning news anchor, following an extensive Washington Post report that detailed his alleged unwanted sexual advances toward women who worked for him. As Columbia Journalism Review's Pete Vernon pointed out, the dismissals mean "two of the most powerful men in morning television have been removed from their positions due to misconduct."

Al Roker, Lauer's colleague for much of his 24-year tenure on Today, appeared shaken while attempting to give the weather report. "I'm still trying to process the news," Roker said.

President Trump was quick to weigh in on the news, using Lauer's termination to extend his war with news organizations to NBC and its parent company, Philadelphia-based Comcast.

According to CNN's Brian Stelter, reporters from both Variety and New York Times had been investigating Lauer for several weeks. Lauer's firing comes just a month after NBC News fired Mark Halperin over sexual harassment allegations, and just Tuesday NPR ousted David Sweeney, its chief news editor, following allegations of sexual harassment made against him by at least three female journalists. They are just the latest in a series of recent allegations that have forced out noted media figures like Charlie Rose, Roger Ailes and Bill O'Reilly.

Lauer interviewed O'Reilly in September, pressing the former Fox News host and suggesting the network wouldn't have fired such an important figure if it didn't have information that backed up the allegations made by several of his former co-workers.

"You were probably the last guy in the world that they wanted to fire, because you were the guy that the ratings and the revenues were built on. You carried that network on your shoulders for a lot of years," Lauer said. "So doesn't it seem safe to assume that the people at Fox News were given a piece of information, or given some evidence, that simply made it impossible for you to stay on at Fox News?"

The 59-year-old Lauer had been host of Today since January 1997, when he replaced Bryant Gumbel. Since then he has won numerous awards and amassed millions of fans across the country. He previously worked in Philadelphia as host of an ill-fated program on Channel 10.

Last year, Lauer signed a two-year contract extension with NBC News for $28 million a year, making him one of the highest earning media personalities on television. He was scheduled to host NBC's live coverage Wednesday night of the Rockefeller Center tree lighting.

Here is Lack's full letter:

"On Monday night, we received a detailed complaint from a colleague about inappropriate sexual behavior in the workplace by Matt Lauer. It represented, after serious review, a clear violation of our company's standards. As a result, we've decided to terminate his employment. While it is the first complaint about his behavior in the over twenty years he's been at NBC News, we were also presented with reason to believe this may not have been an isolated incident.