Here in the UK random, unprovoked attacks on the emergency services (particularly the fire brigade for some reason) are extremely common...common enough that we've had government ad campaigns about it in the past. So whilst I'm not aware of any fatal attacks in the UK it saddens me to say that this story in no way suprises me.
And to answer your question about who the fuck does this sort of thing, I have one word to say:
Chavs.
<Edit> Or whatever the American equivalent is.