Amy Duggar King is shedding light on a distressing part of her family’s past.

In her newly released memoir, Holy Disruptor: Shattering the Shiny Facade by Getting Louder With the Truth, which hit shelves on October 14, the 39-year-old shares allegations of abuse her mother, Deanna, suffered at the hands of her father, Jimmy Lee Duggar.

“Grandpa Duggar was a complicated man,” Amy reflects. She likened him to a real-life Kramer from Seinfeld due to his erratic nature. While she found him humorous, she also described him as “possibly a little insane.” Amy noted that she and her cousins — the 19 children of Jim Bob and Michelle Duggar — were taught to approach him with caution, aware of his “darker side.”

Amy reveals that Jimmy Lee’s own upbringing was marred by an alcoholic father who frequently used him “as a punching bag,” which influenced Jimmy Lee’s own volatile behavior. Deanna, 63, and her brother grew up with “corporal punishment,” and Amy remarked, “There was little distinction between discipline and cruelty, and the line was often crossed.”

She recounted two particularly horrifying episodes. The first incident took place when Deanna returned from college and witnessed her father “yelling violently” at her mother. As Deanna attempted to leave, she was restrained. “With a leather belt in his hand and a terrifying, manic look in his eyes, he grabbed her by the legs, pinned her to the bed, and began to beat her, each strike more forceful than the last,” Amy recounted. The ordeal, which she described as “brutal torture,” lasted over an hour, leaving Deanna “black and blue and beaten to a bloody pulp,” while her grandmother did nothing to intervene.

The second incident took place when Deanna was 21, after Jimmy Lee learned she wanted to move in with her then-boyfriend. Amy wrote, “He grabbed her by the throat, carried her from the kitchen to his bed, and jumped on top of her. He wrapped his hands around her neck, lay on top of her so she was unable to move, and started strangling her. … He almost succeeded in murdering my mother.” Thankfully, Deanna’s mother called for help, and Jim Bob intervened. “Jim Bob might not have known it at the time, but he saved her life that day,” Amy said.

While the physical abuse reportedly stopped after that day, Deanna still experienced “bickering and name-calling.” She warned her own daughter to “never be alone with Grandpa,” and it took years for Amy to understand why. “The reason I was not allowed to be alone with my grandpa was because he was a predator!” Amy wrote. “Underneath JL’s charming and funny personality was a true monster.”