"She's f---ing over the FBI. How stupid is that?" former president Bill Clinton roared into the phone.

He had just learned that Hillary – who was under investigation for using an unauthorized, unsecured private email server while she was secretary of state and deleting more than 30,000 emails before turning her server over to the Justice Department – was cracking jokes about the biggest scandal of the election.

On Aug. 15, 2015, Hillary joked about the investigation into her email scandal during a speech to 2,000 people at the Iowa Democratic Wing Ding in Clear Lake, Iowa.

"You may have seen that I recently launched a Snapchat account," she told the crowd. "I love it. I love it. Those messages disappear all by themselves."

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But Bill wasn't laughing, according to a 20-something intern who says she witnessed the troubled former president make a phone call about the predicament.

The intern's story was reported in "Guilty As Sin," a new book by journalist Edward Klein released Tuesday.

The woman, who worked at the William J. Clinton Presidential Library and Museum, said the ex-president maintains close relationships with young library interns, often flirting with them and inviting them up to his private penthouse at the library for wine and massages. She said he also openly fantasizes about hosting naked pool parties on the roof of the library.

"When he talks to you, it's like you are the only person in the world," she said, according to the New York Post. "I always called him Mr. President, naturally, but one day he looked at me with this [lustful] look and said, 'Call me Bill.' I sort of knew that I was in.

"I know what people would say if they knew I gave him a foot massage. But, hey, if it makes him happy, I'm happy to do it. The idea of touching the president of the United States that way is incredibly exciting to me."

Get Edward Klein's hot new release, "Guilty As Sin: Uncovering New Evidence of Corruption and How Hillary Clinton and the Democrats Derailed the FBI Investigation."

In fact, the woman said she had been massaging Bill's feet when the ex-president received a phone call, according to the Post.

"Damn!" he exclaimed, as he set the phone down.

"What's wrong?" the intern says she asked.

"Hillary just told a bunch of Iowa Democrats she's on Snapchat," he said.

"So what?" the woman replied. "I'm on Snapchat. Everybody's on Snapchat."

"Yeah, but she said she loves Snapchat because all her emails disappear by themselves," Bill reportedly explained.

"I still don't understand," the intern replied.

"Just keep doing what you're doing," he told her, according to the Post.

While the woman continued massaging the former president's feet, he made another phone call.

When someone answered, he informed the person that Hillary was making jokes about her disappearing emails.

"She's f---ing over the FBI. How stupid is that?" he said. "You and I need to talk. I'll send a plane to get you."

The Post reported, "The man who arrived at the library was one of Bill Clinton's oldest and most trusted advisers. [The source was interviewed more than two dozen times for this book.] They strolled out onto Clinton's penthouse terrace, his friend carrying a tumbler of Johnnie Walker Black, Bill with a glass of red wine, which his doctor had prescribed for his heart."

The adviser says he told Bill, "You're right. This email thing is spiraling out of control."

He continued, "From what I know of the case, she's extremely vulnerable. It involves not only the FBI and the Justice Department, but two inspectors general in the intelligence community and the inspector general of the State Department. There are a number of statutes that she appears to have violated and national security laws that she may have breached."

That's when the adviser presented several sheets of paper and read from a detailed list that the Post reports "amounted to a bill of indictment."

Get Edward Klein's hot new release, "Guilty As Sin: Uncovering New Evidence of Corruption and How Hillary Clinton and the Democrats Derailed the FBI Investigation."

After the adviser finished reading the items, Bill asked, "So?"

"My recommendation is that Hillary get ahead of the situation by hiring an outside legal counsel," the adviser reportedly said. " She needs to secure the services of an expert legal counsel – preferably a big-league defense attorney from the Republican side of the aisle."

According to the Post, he warned Bill that Hillary needed to obtain some "discovery" to figure out where the probe was headed.

"You don't want to be blindsided, and if you ignore it, pretend it's a partisan ploy, and act scornfully, it will blindside you," the adviser said. "That's not where you want to be."

The adviser told Klein, "Hillary's emails aside, there was a big problem with her campaign. Bill knew – even if Hillary didn't – that he had to be a major component of her campaign for it to work. ... But he was far from certain that he had the stamina to do as much campaigning as needed to be done.

"The other component was the growing distance between Bill and Hillary. She didn't listen to much of what he said anymore. When he went on about policy and politics, she rolled her eyes and started checking messages on her Blackberry.

"She resented the fact that Bill was treated like a rock star and that she had to work hard to create the illusion of enthusiasm. All Bill had to do was walk into a room. He gave off an electrical charge. Men lit up in his presence. Women swooned. Hillary had to scream to get attention."

Nonetheless, less than a year after Hillary cracked her email jokes in Iowa, Bill was busy arranging to "bushwhack" Attorney General Loretta Lynch on the tarmac at the Phoenix airport, according to another bombshell from Klein's new book. Lynch had been presiding over the DOJ as it determined whether to prosecute Hillary.

Klein revealed that Bill learned from a Secret Service agent that Lynch was about to land, so he instructed his pilot to abort his plane's takeoff.

"Don't take off!" he shouted, according to the London Daily Mail.

Minutes later, Bill met with Lynch for a half hour.

A Clinton adviser told Klein the former president said, "I want to bushwhack Loretta. I'm going to board her plane. What do you think?"

The adviser continued, "He knew it would be a huge embarrassment to Loretta when people found out that she had talked to the husband of a woman – the presumptive nominee of the Democratic Party – who was under criminal investigation by the FBI.

"But he didn't give a damn. He wanted to intimidate Loretta and discredit [FBI Director James] Comey's investigation of Hillary's emails, which was giving Hillary's campaign agita."

The Daily Mail reported: "The adviser, who was not on the plane, said Clinton told him later that he noticed 'beads of sweat' on Lynch's upper lip as she and her husband listened to the former president talk – sending a message that Hillary had a power base that included 'the full weight of the Clinton machine, the Democratic Party, and the White House.'

'Bill said he could tell that Loretta knew from the get-go that she'd made a huge mistake,' the adviser said.

"'She was literally trembling, shaking with nervousness. Her husband tried to comfort her; he kept patting her hand and rubbing her back.'"

Just one week after their meeting, Comey told the nation that Hillary and her aides had been "extremely careless in their handling of very sensitive, highly classified information." But the FBI would recommend no charges against the former secretary of state.

Get Edward Klein's hot new release, "Guilty As Sin: Uncovering New Evidence of Corruption and How Hillary Clinton and the Democrats Derailed the FBI Investigation."