Former Democratic presidential nominee Hillary ClintonHillary Diane Rodham ClintonHillary Clinton to Trump ahead of Putin summit: 'Do you know which team you play for?' 10 things we learned from Peter Strzok's congressional testimony Get ready for summit with no agenda and calculated risks MORE says she was "dumbfounded" when she learned then-FBI Director James Comey was renewing the investigation into her private email server just days before the election.

"I was just dumbfounded. I thought, what is he doing? The investigation was closed. I know there's no new information. I'd certainly given everything of any relevance to them," Clinton said on NBC's "Today" on Wednesday. 

"Then it became clear, this was not necessary, he could have called me up, he could've called others involved and said 'Hey, can we look at this new stuff and make sure its stuff we've seen before?' Absolutely. Have at it," she continued. 

"But no, he had to write letters to Congress, of which immediately were leaked. So I feel very strongly that he went way beyond his role in doing what he did," she said. 

Clinton also said Comey's intervention played a major role in the outcome of the election. 

"I think the determining factor was the intervention by Comey on Oct. 28," she said. 

"It stopped my momentum, it drove voters from me — understandably. This is not about the voters, who were saying, 'Well, wait what does this mean and how do I evaluate it?' And so I think that in terms of my personal defeat was the most important factor," she said. 

Clinton's comments come a day after the launch of her new book recounting her experience during the 2016 presidential race, "What Happened." 

While the former nominee says she takes responsibility for her shocking loss to President Trump in the book, she openly questions the actions of various characters such as Comey, her former primary rival Sen. Bernie SandersBernard (Bernie) SandersOn paper, Wilkie is the perfect candidate for VA secretary, but his qualifications go further Sacha Baron Cohen mulls arming toddlers with guns in inaugural episode Ocasio-Cortez to campaign with Bernie Sanders in Kansas MORE (I-Vt.), former President Barack ObamaBarack Hussein ObamaObama in Kenya for launch of sister’s sports center Get ready for summit with no agenda and calculated risks US envoy to Russia: 'Highly unlikely' that Trump will recognize Russia annexation of Crimea MORE and former Vice President Joe BidenJoseph (Joe) Robinette BidenBiden: I’m ‘ashamed’ of Trump’s border policies Biden to ramp up campaigning for Dem candidates after Labor Day: report California Dems endorse progressive challenger over Feinstein MORE.