Jack Schlossberg, the only grandson of President John F. Kennedy, was not among the many people poring over the new trove of government files about Kennedy’s assassination when it was released on Tuesday. Instead, Mr. Schlossberg was on social media criticizing President Trump, Republican lawmakers and the news media over the handling of the files.

Mr. Schlossberg, 32, the son of the president’s daughter, Caroline Kennedy, and an outspoken voice in Democratic politics, has long been a critic of the Trump administration and its policies. During last year’s election cycle, he made a series of comedic TikTok posts that mocked Republican candidates, as well as his second cousin, Robert Kennedy Jr., who was then running for president as an independent. But the unsealing of 64,000 pages of files about his grandfather’s assassination, under an executive order from President Trump, made the political personal.

In a series of posts on X that were fiery even by Mr. Schlossberg’s standards, he said that the Trump administration did not give anyone in President Kennedy’s family a “head’s up” before the documents were released. “A total surprise, and not shocker!!” he wrote.

The Trump administration did not immediately reply to a request for comment about Mr. Schlossberg’s assertion that the Kennedys had not been advised on the release ahead of time.

Beyond his own online thread about the files, Mr. Schlossberg also took issue with a post on X from Mike Lee, the senior senator from Utah and a Republican, who asked the question, “Why did it take so long to release the JFK files?” Mr. Schlossberg responded, “You really care about JFK’s legacy? You’re dismantling it.”

Mr. Schlossberg, who was hired last July as political correspondent for Vogue, was also critical of the news media’s extensive coverage of the decades-old documents. Standing in front of a wall-mounted TV tuned to CNN, in which the political correspondent Harry Enten and the anchor Erin Burnett were discussing the J.F.K. files as breaking news, Mr. Schlossberg said in a video post, “There’s so much actual news. Why are you covering this? … Stop.”

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