Presumptive Democratic presidential nominee Hillary Clinton is said to have once thrown a Bible at the back of a Secret Service agent's head in rage.

This alleged incident, among many others, are revealed in an upcoming book titled "Crisis of Character," written by former Secret Service uniformed officer Gary J. Byrne. Byrne was detailed at the White House for eight years in the '90s, three years of which he was posted outside the Oval Office.

"The First Lady had a different sort of liveliness," Byrne says in an excerpt of the book, as quoted on Breitbart. "She once threw a Bible at an agent on her detail, hitting him in the back of the head. He bluntly let her know it wasn't acceptable. He told me that story himself."

Clinton told The New York Times in June 2014 that she "was raised reading the Bible, memorizing passages from it, and being guided by it." It has a huge influence on her thinking, she said, and is a "source of wisdom, comfort and encouragement."

According to the Breitbart report, Byrne's book details how, the more "at home she felt in the White House," the pattern of rage Clinton exhibited became more regular and "it got worse" over time. She is said to have "vented on everyone" and treated her security detail as "furniture."

"Most of us knew to brace for her inevitable eruptions," Byrne wrote. "They didn't happen every day, but behind closed doors we learned about them fast. In public, she was everyone's best friend. Privately, she was her normal self."

The book also contains stories experienced by Uniformed Officers, one of which said that the then-first lady told him to "go to hell" and the other one was told to "go f*** yourself." The author said that being assigned to be in Clinton's detail "was a form of punishment handed down by passive-aggressive middle management."

Moreover, it narrates how, in a tantrum, Mrs. Clinton allegedly yelled at her husband, then-president Bill Clinton, saying that they "need to get rid of these a**h***" -- referring to Secret Service's Uniformed Division -- who she claimed to have been conspiring against them. Byrne wrote that "careers were made or broken" depending "on the whim" of her "wrath."

"Hillary's antics made my job interesting," Byrne said. "She'd explode in my face without reservation or decorum..."

Breitbart says that Clinton's team has been trying find ways to undermine Byrne and his upcoming book, but because many of those allied with the Clintons have praised him during his time with the military and law enforcement, it would be difficult for them to discredit him.

"Crisis of Character: A White House Secret Service Officer Discloses His Firsthand Experience with Hillary, Bill, and How They Operate" will hit the shelves on June 28.