Some of President Trump’s harshest critics within the GOP castigated the president Monday after he published a post declaring that the murder of the filmmaker, Rob Reiner, and his wife, Michele Singer Reiner — allegedly at the hands of their son — resulted from anger that Reiner caused due to his “Trump Derangement Syndrome.”

“Regardless of how you felt about Rob Reiner, this is inappropriate and disrespectful discourse about a man who was just brutally murdered,” a longtime Trump opponent, the Republican congressman from Kentucky, Thomas Massie, posted on X alongside a screenshot of the president’s comments.

Mr. Massie, who will face a primary challenge by a Trump-backed candidate next year, also defied his colleagues to speak up against the president’s rhetoric.

“I guess my elected GOP colleagues, the VP, and White House staff will just ignore it because they’re afraid? I challenge anyone to defend it,” he said.

In the widely critiqued TruthSocial post, the president wrote that the acclaimed director failed to see the “new heights” his administration has achieved, which prevented him from recognizing America’s “Golden Age.”

“A very sad thing happened last night in Hollywood. Rob Reiner, a tortured movie director and comedy star, has passed away, together with his wife, Michele, reportedly due to the anger he caused others through his massive, unyielding, and incurable affliction with a mind crippling disease known as TRUMP DERANGEMENT SYNDROME,” Mr. Trump wrote.

He then railed against Reiner — who was a long-time and vocal critic of the president — for his outspokenness, before ending the post saying, “rest in peace.”

“He was known to have driven people CRAZY by his raging obsession of Donald J. Trump, with his obvious paranoia reaching new heights as the Trump Administration surpassed all goals and expectations of greatness, and with the Golden Age of America upon us, perhaps like never before,” he wrote. “May Rob and Michele rest in peace!”

Outgoing congresswoman Marjorie Taylor Greene, who previously had been one of the president’s most fervent supporters before a very public falling out, criticized Mr. Trump for politicizing the tragic murder.

“This is a family tragedy, not about politics or political enemies,” she said in a post on X. “Many families deal with a family member with drug addiction and mental health issues. It’s incredibly difficult and should be met with empathy especially when it ends in murder.”

Mr. Trump’s post also raised ire from some of the most devoted rank-and-file MAGA supporters.

“I’m struggling to believe this is real or that the greatest President the US will ever have actually wrote these words, much less tapped send,” one user commented on X.

“I love you but this is seriously distasteful,” said one user on Truth Social in a reply to Mr. Trump’s post.

On Monday, police arrested the Reiners’ son, Nick Reiner, on suspicion that he stabbed the couple to death during a heated argument. The couple was found Sunday by their daughter, Romy.

With Democrats rushing to criticize the president for his remarks, other Republicans did not address Mr. Trump’s comments, but posted their condolences, as did several of the president’s celebrity fans, including some who had worked with Reiner.

“While I disagreed with Rob politically, vehemently at times, no one deserves the ending he and Michele received. No one. Tragic. Disgusting. Obscene. And devastating beyond words for their family,” wrote Representative Nancy Mace.

“Rob and I remained good friends ever since we made GHOSTS OF MISSISSIPPI. The studio didn’t think I was old enough to do the part, but Rob fought for me,” actor James Woods wrote in a post on X. “Political differences never stood in the way of our love and respect for each other. I am devastated by this terrible event.”