The Secret Service is “aware” of a tweet attacking President Trump’s adolescent son that was posted by the actor Peter Fonda, a spokesman for the agency said on Wednesday.
“We should rip Barron Trump from his mother’s arms and put him in a cage with pedophiles,” Mr. Fonda wrote in all caps, referring to the president’s 12-year-old son, in a recent post on Twitter that was later deleted. Mr. Fonda, 78, also wondered if such an act would prompt the first lady Melania Trump to “stand up against” her husband.
The spokesman for the agency said that “as a matter of practice, the Secret Service does not confirm the existence or the status of an investigation.”
In recent days, Mr. Fonda has used Twitter to urge mass protests and to rail against the Trump administration’s “zero tolerance” policy, which has separated immigrant children from parents who crossed illegally into the United States, a practice that drew wide-ranging criticism from both parties, including Mrs. Trump. On Wednesday, Mr. Trump signed an executive order intended to end the separation of families at the border by detaining parents with their children for an indefinite period.
Mr. Fonda’s tweet “is sick and irresponsible,” Stephanie Grisham, a spokeswoman for Mr. Trump, said in an email on Wednesday. She said the tweet had been reported to the Secret Service.
His tweet also drew backlash from some on the right, including the president’s eldest son. Donald Trump Jr. responded to Mr. Fonda in a series of tweets on Wednesday, at one point calling Mr. Fonda a “sick individual,” “bully” and “coward.”
Mr. Trump Jr. also compared Mr. Fonda with Roseanne Barr, the comedian and actress whose racist tweet last month led ABC to cancel her hit sitcom. Mr. Fonda — an Oscar-nominated actor, the son of Henry Fonda and younger brother of Jane Fonda — appears in the coming film “Boundaries,” which is being distributed by Sony Pictures Classics and is scheduled to be released Friday.
“I wonder if they will apply the same rules” to Mr. Fonda and Ms. Barr, Mr. Trump Jr. said in another tweet. “I have a strange suspicion that they wont do anything.”
In a statement on Wednesday evening, Sony Pictures Classics called Mr. Fonda’s comments “abhorrent, reckless and dangerous.”
“We condemn them completely,” the statement went on. “It is important to note that Mr. Fonda plays a very minor role in the film. To pull or alter this film at this point would unfairly penalize the filmmaker Shana Feste’s accomplishment, the many actors, crew members and other creative talent that worked hard on the project.”
Mr. Fonda issued an apology later Wednesday, saying in a statement that he had tweeted “something highly inappropriate and vulgar about the president and his family.”
“Like many Americans, I am very impassioned and distraught over the situation with children separated from their families at the border, but I went way too far,” his statement said. “It was wrong and I should not have done it. I immediately regretted it and sincerely apologize to the family for what I said and any hurt my words have caused.”
Earlier this week, Mr. Fonda also directed vulgar tweets at Kirstjen Nielsen, the secretary of homeland security, and Sarah Huckabee Sanders, the White House press secretary, calling them both liars.
He said that Ms. Nielsen “should be pilloried in Lafayette Square naked and whipped by passersby” and that Ms. Sanders’s children should perhaps be taken away from her. The tweets have since been deleted.
Representatives for the Department of Homeland Security, the White House and Ms. Sanders did not immediately respond to a request for comment, nor did a spokesman for the Secret Service.
A spokeswoman for Mr. Fonda said his previous statement applied to his remarks about Ms. Nielsen and Ms. Sanders as well.
Mr. Fonda is not the first celebrity to publicly lash out at President Trump or his family.
In May 2017, the comedian Kathy Griffin was photographed posing with a mask styled to look like the severed, bloody head of Mr. Trump. She was condemned by the president and fired as co-host of CNN’s New Year’s Eve program.
Last month, the late-night host Samantha Bee apologized for using a vulgar epithet to describe Ivanka Trump, the president’s eldest daughter, on her TBS show. And earlier this month, the actor Robert De Niro, a longtime critic of Mr. Trump, stood onstage at the Tony Awards and shouted a vulgarity about the president into the microphone.