Eric lashed out at the New York Attorney General after she filed a lawsuit accusing him and his family of years of business fraud.
He wrote on Truth Social that Letitia James was the most corrupt Attorney General in US history.
Donald Trump's son, who is an executive vice president of the Trump Organization, posted a video of James that shows her saying "his days are numbered."
She promised to investigate Donald Trump when she was running for attorney general. She said on the day after she was elected that she was going to file a lawsuit.
There are over 200 instances of false and misleading valuations of the former president's assets according to the lawsuit.
According to James' office, Trump inflated his net worth to further enrich himself and cheat the system.
State and criminal law may be involved in the conduct detailed in her suit. The allegations will be referred to the US attorney for the Southern District of New York.