The Gilded Age.”In a letter to HBO Chief Content Officer Casey Bloys, People for the Ethical Treatment of Animals (PETA) cited whistleblower reports that a 22-year old horse with possible health issues died last week during filming of the historical drama in Nassau County.“We’re calling on HBO to…hold the party or parties who allowed it to occur responsible,” Courtney Penley, coordinator for animals in film & television for PETA, wrote. “Finally, we’re asking you to take measures so that something similar never happens again.”After the letter was shared with the media, HBO confirmed that a horse had died on the set on June 28 during filming, but said it was “likely of natural causes, according to a veterinarian’s preliminary findings.” “The safety and well-being of animals on all our productions is a top priority, and the producers of ‘The Gilded Age’ work with American Humane to ensure full compliance with all safety precautions,” HBO added.