Brian William's recollection of an event that took place in March 2003, when he was a passenger with a group of U.S. military helicopters traveling in the skies above Northern Iraq, has quickly evolved back into what it appears to have been from the start - a lie.

The seasoned "NBC Nightly News" anchor announced last week that he made a mistake in recalling the attack on the helicopters, and voluntarily stepped down from the position he has held for more than 10 years.

But yesterday, NBC News president Deborah Turness announced in a memo to all staff that Williams was suspended for six months, without pay, effective immediately.  His accounts of the attack remain under review.

Nearly 12 years ago, at the start of Operation Iraqi Freedom, Williams reported from the front lines of the war and relayed the details of the day's attack to colleague Tom Brokaw, whom he would replace just a year and a half later.

With alleged video of the incident rolling, Williams says, "Radio traffic makes clear this routine mission is running into trouble.  We quickly make our drop and then turn southwest.  Suddenly - without knowing why - we learned we've been ordered to land in the desert. On the ground, we learn the Chinook ahead of us was almost blown out of the sky."

Launched from the ground, a rocket-propelled grenade, or RPG, pierced the Chinook but failed to detonate. 

But Williams was not in that helicopter and several military personnel that were don't recall his aircraft being part of that convoy.

Reporting from the Nightly News desk on Jan. 30, Williams did a story on Command Sergeant Major Tim Terpak, a three bronze star military veteran he took to a New York Rangers hockey game.

By choosing a very public way of thanking Terpak, who had been assigned to protect Williams and the NBC crew traveling with him in 2003, the news anchor once again had opportunity to talk about his near fatal helicopter ride.

But something was off, and this time people began to notice. 

As social media lit up with comments about the story and links to pictures of Williams and Terpak sitting together at Madison Square Garden, others veterans who were part of that mission in 2003 remembered things differently.

On Facebook, where the NBC page included a video of the story, one comment in particular caught Williams' attention.

"Sorry dude, I don't remember you being on my aircraft," wrote Lance Reynolds, identified by military newspaper Stars and Strips as a flight engineer on the downed helicopter. "I do remember you walking up about an hour after we had landed to ask me what had happened."

Williams was not in the helicopter that had been shot down, Reynolds and other crew members quickly told Stars and Strips.

"You are absolutely right and I was wrong," Williams replied on Facebook.

In an interview with Stars and Stripes, Williams said he had misremembered the events and was sorry.

"I would not have chosen to make this mistake," Williams said. "I don't know what screwed up in my mind that caused me to conflate one aircraft with another."

The disclosure of the details of his story not only calls Williams' integrity into question but also points a finger at NBC, a trusted news source that has repeated the false claim for nearly 12 years.

On Monday, the New York Times questioned the reliability of the human memory and posed the question, "Was Brian Williams a victim of false memory?"

"Memory is a reconstructive process, and we are drawing on multiple sources of information," Steven J. Frenda, a postdoctoral research fellow at the New School for Social Research, told the New York Times.  "A false memory can arise when we mistakenly attribute some other information as a memory. Whether you've exaggerated something in the past, or it's something else you've seen or experienced, you can pull that into what you consider to be the truth."

While Williams' memory may be failing him or the traumatic events of the attack may have left him confused, he is first and foremost a journalist - not a storyteller.  And the facts of the news story he first told in 2003 have evolved and been exaggerated over time.

Williams may prove to be his own worst enemy in this debacle.  His embellishments can easily be tracked thanks to his status - not as a hard-hitting journalist - but as a celebrity.

In March 2013 - 10 years after the incident - Williams once again told the story in increasingly vivid detail during an appearance on "Late Night with David Letterman."

"We were in some helicopters and what we didn't know was we were north of the invasion," he told Letterman.  "We were the northern most Americans in Iraq.  Two of our four helicopters were hit by ground fire, including the one I was in, by RPG and AK47."

Even if Williams is the victim of false memory, a quick review of the segment with Brokaw in March 2003 would have made it clear to him.  A Chinook was hit by an RPG and he was not in that Chinook.