In the hours since, social media has been flooded with messages of grief from friends and fans of Reiner, as well as backlash to a Truth Social post from President Donald Trump, who'd written that the director was "tortured and struggling" and suggested that he'd died from a "mind crippling disease known as TRUMP DERANGEMENT SYNDROME."

Rob Reiner, the son of a comedy giant who became one himself as one of the preeminent filmmakers of his generation with movies such as “The Princess Bride,” “When Harry Met Sally …” and “This Is Spina...