Footage has emerged of a baby elephant being rescued in a four-seater lightweight plane, after the rest of its 100-strong herd was slaughtered by poachers.
The baby animal, which rescuers nicknamed Max, was the only surviving member of the herd after the massacre.
Roberts flew the elephant to safety in his plane, and his colleague David Gates filmed the journey. The elephant can be seen being offered water and stroking Roberts' head.
Directors of the national park heard about a massacre of elephants and asked Roberts to go to the scene as he was nearby, he told BBC World Service.
Roberts followed elephant tracks and saw the "massacre zone" which was covered with elephant bones as the poachers had removed the meat from the elephants.
"It's just gut-wrenching when you see something of that extent, you know, whether it's in a war when humans are taken down or whether it's where animals are taken down," he told BBC World Service. "It's still just a sinking feeling in your ceiling. It's terrible."
Max the baby elephant sadly later died as a result of the experience he had gone through.