I never saw this, but I live in Essex, I drive Underground trains, but the line I work on is more in the open, i've had a bullet come through my cab window, and before they covered the bridges, we used to cover our heads as we went under them.
This sort of thing is all too prevalent all over the country, and its been going on for far too long,
Also, objects are often placed on the tracks, its a wonder that no-one was seriously injured before this, it'll happen again.
My thought are with this chap and his family, I just hope his train company look after him.
As for the people who did this, not neccessarily, but probably youths, I don't know what can be done, if they are caught, they should be made to go to this chaps house to see first hand what they've done.