That a crowd of thousands gathered for the funeral of Kelvin Kiptum was a testament to the marathon world record holder's staggering impact on his sport.Kiptum's death in a road accident at the age of 24 has left a gaping hole in the distance running community, not least in his native Kenya."You ask yourself so many questions as to why, but sometimes it's hard to get answers," double Olympic gold medalist David Rudisha tells CNN about his compatriot's untimely death.According to police, Kiptum and his coach Gervais Hakizimana died at the scene of a crash outside the town of Eldoret in the Rift Valley.The star athlete broke the world record in just his third marathon race last year, running a time of two hours and 35 seconds in Chicago, and a few months before that had set a course record in London.In the year ahead, Kiptum had hoped to become the first man to run under two hours over the 26.2 miles of the marathon, as well as being a strong favorite to win gold at the Paris Olympics.Even in a country renowned for producing world-class runners, Kiptum was a once-in-a-generation athlete, achieving so much in such a tragically short career."The last few weeks have been a really sad moment for Kenyans," says Rudisha, himself a world record holder over 800 meters. "To lose such a talented, young athlete, it's not easy."Kelvin was very special, coming up and running just three marathons, all of them under two hours, two minutes. That really shows how talented he was."In breaking Eliud Kipchoge's old world record of 2:01:09, Kiptum eclipsed a man many believed to be the greatest of all time – and he did so with apparent ease, effortlessly pulling away from his rivals in the closing stages of major marathons.He never had a chance to race the 39-year-old Kipchoge, but it was obvious that Kiptum would go on to succeed his compatriot as the standout distance runner of his generation."He was very determined," says Rudisha, "and you were expecting good things to come from him in the future … He just came for a short time, not many people knew him, but he was really becoming famous and he was such a lovely young guy."Rudisha, best remembered for breaking his own 800-meter world record at the London 2012 Olympics, last raced in 2017, a year after he defended his Olympic title in Rio.He is now an enthusiastic spectator of athletics meets around the globe, and has high hopes for Emmanuel Wanyonyi, a 19-year-old tipped to win Kenya's fifth-straight gold medal in the 800 meters this year.No athlete has come close to Rudisha's world record in the years since it was set, but the 35-year-old has no qualms about seeing it taken by another athlete at some point in the future."Everybody feels good to watch a world record," he says. "With the future, with the improvement of new shoes, better stadiums … definitely one person will break it. And it will be good also to watch, so that I can also congratulate ."