Isn't there a law to cover acts of recklessness? It is like the motoring offences of careless and dangerous driving, in both cases the driver isn't deliberately trying to kill anyone, but is driving in a way that falls far below the level of competance required in law. It would be very difficult to claim throwing a brick through the window of a moving train was accidental (i.e. carelessness), so it must be an act of recklessness, in which case the perpetrator is a danger to the public and should be sentenced accordingly.