"You should be ashamed of yourself," Trace wrote publicly on Saturday, two days after saying he's "genuinely worried" about the country star's well-being.

The country singer's son wrote a heartfelt open letter on Instagram after that viral inauguration performance: "You’re not healthy Dad and everyone is noticing it."

Just days after Trace Cyrus said he and his sisters were "genuinely worried" about their father Billy Ray Cyrus' health, the 35 year old claims the country music star is threatening legal action against him.