Twenty years ago Robert F. Kennedy Jr. appeared in an HBO documentary about the dangers of a nuclear plant on the Hudson River. Indian Point: Imagining the Unimaginable, directed by his sister Rory Kennedy, pits the crusading Kennedys, pictured flying in a helicopter over the nuclear facility, against Entergy, the power company. The film argued that the surrounding environment would be made uninhabitable if the plant came under terrorist attack.

This was necessarily a high-stakes confrontation. In anticipation, Rory warned her production team they had a potential liability: Her brother, though a prominent and successful environmental lawyer known for suing polluters, could be fast and loose with the facts. “He can say some crazy shit,” she told them, according to a person involved in the film. Kennedy’s interviews had to be thoroughly fact-checked “even though he might come across as an expert,” she said. “That’s who he is.”

Sure enough, the film had already been edited when producers discovered that Kennedy’s interviews were littered with inflated and inaccurate claims, rendering portions of the film unusable. “It was like, Holy shit,” says another source familiar with events. “We have to get the audio and cut certain things out. We can’t really say this. You can be sued!”