In a scathing letter Tuesday, Caroline Kennedy warned senators about her cousin, Robert F. Kennedy Jr., calling him a “predator.”

The letter was sent to lawmakers ahead of Robert F. Kennedy Jr.’s Senate confirmation hearing for the role of secretary of the Department of Health & Human Services (HHS), which is scheduled for Wednesday.

Caroline Kennedy – a former U.S. ambassador to both Australia and Japan and the last living child of former President John F. Kennedy, Robert F. Kennedy Jr.’s uncle – called the role “an enormous responsibility, and one that Bobby is unqualified to fill.”

Caroline Kennedy wrote that she feels “an obligation to speak out” now that Robert F. Kennedy Jr. has been nominated for “a position that would put him in charge of the health of the American people.”

“I have known Bobby my whole life; we grew up together,” she wrote in the letter, in part. “It’s no surprise that he keeps birds of prey as pets because he himself is a predator.”

Caroline Kennedy said she watched family members follow her cousin “down the path of drug addiction,” and shared disturbing details of his alleged behavior with animals.

“His basement, his garage, and his dorm room were the centers of the action where drugs were available, and he enjoyed showing off how he put baby chickens and mice in the blender to feed his hawks. It was often a perverse scene of despair and violence,” she wrote.

She also accused Robert F. Kennedy Jr. of being “addicted to attention and power,” and said he “preys on the desperation of parents of sick children – vaccinating his own children while building a following by hypocritically discouraging other parents from vaccinating theirs.”

Caroline Kennedy further accused her cousin of “[continuing] to grandstand off my father’s assassination, and that of his own father,” saying former President Kennedy “would be disgusted” by his actions.

“The American health care system, for all its flaws, is the envy of the world,” Caroline Kennedy wrote. “Its doctors and nurses, researchers, scientists, and caregivers are the most dedicated people I know. Every day, they give their lives to heal and save others.”

“They deserve better than Bobby Kennedy – and so do the rest of us. I urge the Senate to reject his nomination,” she concluded.