Here's what happened when NBC tried to get Brain Williams to admit he lied

An unnamed NBC source told Vanity Fair about how difficult it was for network executives to get anchor Brian Williams to explain how he misremembered a helicopter ride in Iraq more than a decade ago.

In conversations with his colleagues at NBC, Williams reportedly wondered if "something happen[ed] to [his] head" to make him forget what actually happened in Iraq.

Williams' career derailed earlier this year when he was forced to admit that he exaggerated a story from his coverage of the Iraq invasion.

Earlier this year, Williams said during an NBC broadcast that a helicopter he was flying in was "was forced down after being hit by an RPG" in Iraq. Crew members who were on the helicopter that was actually hit by a rocket-propelled grenade then came forward to say Williams was on another helicopter that arrived at the site later.

As a result of the embellishment, Williams was suspended from NBC for six months and public trust in him has cratered.

Williams blamed his mistake on "the fog of memory over 12 years." He wrote in his apology on Facebook: "I spent much of the weekend thinking I'd gone crazy. I feel terrible about making this mistake, especially since I found my OWN WRITING about the incident from back in '08, and I was indeed on the Chinook behind the bird that took the RPG in the tail housing just above the ramp."

This apology didn't seem to help Williams much, and one NBC source told Vanity Fair that it was difficult to get an explanation out of Williams once stories about his exaggerations began to surface.

"He couldn't say the words 'I lied.' We could not force his mouth to form the words 'I lied,'" the source said. "He couldn't explain what had happened. [He said,] 'Did something happen to [my] head? Maybe I had a brain tumor, or something in my head?' He just didn't know. We just didn't know. We had no clear sense what had happened. We got the best [apology] we could get."

NBC executives had reportedly been aware of Williams' tendency to embellish long before he admitted that he exaggerated the Iraq story, according to The New York Times.

One NBC reporter told the Times that "there was no one around to pull [Williams'] chain when he got too over-the-top."

Another "longtime NBC employee who has worked with Williams on several occasions" told the New York Post earlier this year that "everyone" at the network knew Williams was "a liar."

NBC is now trying to restore morale and stability at the network's news division, according to Vanity Fair.

Bryan Burrough writes for the magazine: "Williams's stunning fall was only the worst of a string of embarrassing episodes that have brought NBC News, long one of the gold standards of television news, to its knees."