Hypothetical. You kill one person and you save a thousand. The system by which decides if they live or die (depending upon your answer) is an universal law (like thermodynamics). It has no free will, no choice, no concept of choice. The method of killing is just pressing a button resulting in an assured death (pick what ever effect you want), a button which you fully understand how it works, and thus there is no possibility of something going wrong. There are only two options, any hesitation, bargaining, reasoning will result in one person dying every second. You are in this situation because of your own mistake, even though it probably was accidental.
Anything I missed?
Anything I missed?