Tom O'Brien was a jockey. The horse racing world mourn his death at the age of 39 after a cancer diagnosis. The Racing Post called him a great person. O'Brien secured victories at the renowned racing event. Several news outlets reported his death after a courageous fight with cancer. At Bangor, a colleague 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 throughout the racing community.