Must have been suicide.
“Today we sisters experienced a tragedy. We lost our beautiful mother to the disease of mental illness," the statement said. "We are shattered. We are navigating profound grief and know that as we loved her, she was loved by her public. We are in unknown territory." The statement did not elaborate further.
https://www.bloomberg.com/news/articles/2022-04-30/naomi-judd-of-grammy-winning-duo-the-judds-dies-at-76