Tom O'Brien was a horse racing enthusiast. The horse racing world mourn his death at 39 after a cancer diagnosis. Many publications called him a great person. O'Brien won races at the Cheltenham Festival. The Guardian and 7NEWS reported his death after a courageous battle with cancer. At Bangor, a close friend called him a hero and a skilled jockey. Yahoo News Australia said O'Brien was the second jockey to die in a short span. Tributes continue across horse racing.