Luis Ansorena and Ernest Riera, who made the documentary. | Teresa Ayuga

Around midday on the seventh of March 2015, the Guardia Civil found the body of a 59-year-old man in a car in the multi-storey car park at Palma Son Sant Joan Airport. The man had been missing for two days, his family having reported his disappearance in El Toro.

He was José Luis Barbero, one of the world's best dolphin trainers. He took his own life after a video was posted online which apparently showed him mistreating dolphins at Marineland, which was where he had worked. A campaign of hate was waged against him on social media. After his death, this ceased. For two documentary filmmakers, Luis Ansorena and Ernest Riera, it was if everything had ended with his death, even though there were many unanswered questions.

They have made a documentary for Netflix - ¿Qué le pasó al rey de los delfines? (What happened to the King of the Dolphins?) - in which they seek answers, not least to ones raised by the 99 seconds of video.

Following the posting of the video, Barbero lodged a 'denuncia' with the courts in Palma against those who could have been responsible for a crime against his honour. Images and sound, he maintained, had been manipulated "with malicious intent". Marineland also filed a complaint for similar reasons, this one with the Guardia Civil's Seprona division.

Luis Ansorena says that "this was a powerful story and it shocked me that the case was falsely closed" (after his death). The film relates how Barbero "came from nothing and reached the top" in his particular field. Ansorena and Riera talked to family, fellow workers and activists. Some were willing to be included in the film, others not. In the latter category was a worker who had told Aspro (the Marineland company) that dolphins were being mistreated and was dismissed. She, it would seem, helped to take the video.

Marineland told Ansorena and Riera that the video had been recorded in a neighbouring apartment. Ansorena went to see the owner: "She threatened to denounce me. Many of those involved said they were afraid and didn't want to speak. My curiosity was aroused by the reluctance from everyone." He regrets that Aspro was among those who didn't want to participate.

* The documentary was released on Netflix on November 25.