Any violent crime is horrible, but this type falls into "worst nightmare" category for me... which is when a completely innocent and unknowing person inadvertently crosses the path of a predator. To imagine living your life, everything is completely normal, just as any other day, and in the matter of seconds, you have been taken by a predator. In these cases I can only hope that the victim becomes unconscious (and therefore unable to know what is happening to them) very quickly.
For different reasons, I know what its like to be unconscious for something horrible - I was hit by a car while crossing the street as a child. One moment I was excited to get home after school, and the next, I was in a hospital. I felt and remember absolutely nothing of the actual impact of the car, which left me in a coma for several days.