Assume you are on a bridge overlooking the track. Ahead, five people on the track are at risk. You can save them by throwing down a heavy object into the path of the approaching train. One is available beside you, in the form of a fat man. Is it O.K. to push him to save the five?
The question makes no sense.
It is not possible to stop trains quickly. They are like ships, they take a long time to speed up or slow down.
An uncle of mine was in a Chevrolet car that met one on a level crossing, and the car was carried several hundred meters before the train, under emergency braking, came to a stop.
A body, even of a very large very fat person, is unlikely to make any difference to a train.
So from that aspect – the question is nonsense.
And I agree with Mike – actively killing anyone is called murder (except if one is employed by the military, industrial, political complex, in which case it is often called patriotism – and that is a different issue).
I would go further, and say that not doing something, that the doing of could have saved a life, is a close second to murder. Which is what the question seems to be hinting at.
There are no simple answers to many sorts of real world questions.
Often people are operating from different paradigms.
The options that occur as real possibilities to people are very much determined by the paradigms that people are operating from.
From the paradigm that I am using, there is no reason for anyone to attack anyone else.
Most of the problems in the world seem to stem from an attachment to a market valuation system.
Market systems have great utility in allocating scarce resources, but by definition cannot deal meaningfully with abundance, and certainly are not incentivised to deliver abundance (markets and market valuation is grounded in asymmetric distribution of resources).
We have the technical capacity to deliver abundance of all necessary resources to everyone on the planet, with very little requirement for people to “work”.
We can deliver freedom and resources to all, but there is no economic incentive to do so (and massive economic incentive not to do so).
Knowing this, how many deaths are happening now, because of the paradigms that are being promoted by people who should know better, but cannot make money from saying what they know?
It is a very deep question, even if, on the surface, it is a nonsense question.