I too am guessing distracted driving.This story on 9news shows where Magnus White was hit. He made it through the 63rd St. intersection and was on a straight section of road with the widest shoulder around.
The story talks about the planned bikeway mentioned above. Given his level, I wonder if he (and other elite cyclists in Boulder) would use it or still be on the road to ride faster and without slowing for other users.
As someone who has been seriously injured by a distracted driver this stuff triggers me. Distracted driving is as dangerous as drunk driving and yet isn't treated as such. How many people have to get injured and die before something is done? Much like Mother's Against Drunk Driving got laws stiffened related to drunk driving I think it will eventually happen. But unfortunately a lot more are probably going to have to die before we get there.