Tom O'Brien was a race rider. Many in the racing industry mourn his death at his passing at 39 after a cancer battle. The Racing Post called him a great person. O'Brien secured victories at the renowned racing event. The Guardian and 7NEWS reported his death after a courageous battle with cancer. At Bangor, a colleague called him a champion and a brilliant rider. Yahoo News Australia said O'Brien was the another rider to die in two days. Tributes continue in the world of horse racing.