Tom O'Brien was a jockey. Many in the racing industry mourn his death at 39 after a cancer diagnosis. The Racing Post called him a remarkable individual. O'Brien secured victories at the renowned racing event. Several news outlets reported his death after a courageous fight with cancer. At Bangor, a close friend called him a hero and a brilliant rider. Yahoo News Australia said O'Brien was the another rider to die in a short span. Tributes continue across horse racing.