WASHINGTON - JUNE 22: Moderator Brian Williams watches a video which pays tribute to late moderator Tim Russert during a taping of "Meet the Press" at the NBC studios June 22, 2008 in Washington, DC. Williams announced that former Nightly News anchor Tom Brokaw would temporarily host the show through the presidential elections in November, 2008. (Photo by Alex Wong/Getty Images for Meet the Press) (Photo by Alex Wong/Getty Images for Meet the Press)

WASHINGTON (CBS DC) — When asked to admit allegations of lies about his war reporting in Iraq, embattled NBC News anchor Brian Williams reportedly deferred blame to a “brain tumor.”

A new Vanity Fair piece details Williams’ fall from the NBC “Nightly News” anchor chair, alleging that he has been unable to explain how he misremembered a helicopter ride in Iraq more than a decade ago. In conversations with his network colleagues, Williams reportedly said “something” may have happened to his head.

“(He said,) ‘Did something happen to [my] head? Maybe I had a brain tumor, or something in my head,’” an NBC insider told the magazine in its upcoming edition. “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.”

The alleged Williams explanation to NBC colleagues follows the scandal exposed by military publication Stars and Stripes, which said he greatly exaggerated his role in a story covering the 2003 Iraq invasion. His NBC broadcast claimed the helicopter he was in “was forced down after being hit by an RPG.” But several crew members on the helicopter actually hit by the rocket-propelled grenade stepped forward and said Williams was on a completely different helicopter and arrived safely at a later time.

Williams was suspended for six months from NBC in February, and said on-air he “misremembered” the incident.

Now a series of NBC insiders tell Vanity Fair that he had a penchant for bureaucratic infighting at the network, and had an aversion to “heavy” news. Williams is also described as insecure that he’d never been a war or foreign correspondent, including accusations that he embellished his account of floating bodies in post-hurricane Katrina New Orleans in 2005.

“He didn’t want to leave New York,” a onetime NBC executive told Vanity Fair. “Getting him to war zones was real tough . . . but when he did go, he came back with these great stories that kind of put himself at the center of things.”

When Williams attempted to explain the embellishments, network confidants said he was “shell-shocked” and unable to be of any help.

“He was having a tough enough time coming to grips with the idea that he had gotten it wrong in the first place, slash misrepresented it, slash lied,” an insider said. “He wasn’t anywhere in the ballpark of being helpful about what had happened 12 years ago.”