The user stated his father had passed away in a series of postings that have since been deleted, and it called President Joe Biden a race slur.
Less than an hour later, the posts were removed from the page, which has 10 million followers.
According to the Trump Organization, the account was compromised.
A message said, "I'm sad to announce that my father, Donald Trump, has passed away. I will be running for president in 2024."
One thread mentioned "some interesting messages" with notorious sex offender Jeffrey Epstein, while another stated North Korea was "about to get smoked."
Others brought up YouTuber Logan Paul and cryptocurrency influencer Richard Heart, who is charged with fraud by the Securities and Exchange Commission.
Posts started appearing at about 8:00 ET.
While his son's account claimed his death, his father wrote an unrelated statement on his Truth Social profile.
According to Trump's spokesman Andrew Surabian, "Don's account has been hacked," adding that the post was "obviously not true."
Since then, Trump Jr. has written on X, formerly known as Twitter, that he has not mentioned his account being compromised other than to "like" a tweet claiming to be his.
We've reached out to X for a response. The company's press email automatically responds with the message "Busy now, please check back later."
Trump Jr. has kept using the Elon Musk-owned website.
The former president launched Truth Social after his X account was shut down in 2021 because of the potential for inciting violence. It was later restored in November of last year.
In a $44 billion agreement, Musk acquired ownership of Twitter in October 2022, renaming it X.
What are your thoughts on the security of high-profile social media accounts, considering the recent hacking of Trump Jr.'s account?
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