One person can only be on the spot for one number. As soon as more than one gets killed, that would mean that the trolley has traversed some distance, which implies that it has killed an infinite number of people. That is impossible in any finite timespan under the aforementioned assumption. Thus the only logical conclusion is that it gets stuck after the first person is killed, at the exact spot the first number is mapped to.

I guess there could also be a different solution when you look at the problem from a different angle. Treating infinity with this little mathematical care tends to cause paradoxes.