There are genetically based heart anomalies primarily among Blacks that causes this every once in a while - can be the greatest athlete in the world prior to the moment it kills you.
It's really rare but every time it happens it gets a lot of publicity.
I'll have to take your word for that right now, but I've read about many white athletes who have died suddenly when they were considered to be in excellent physical health. Pete Maravich comes to mind, and many high school and college athletes as well.