The categorical order and entry into the shelter

In the SD
Many argue that a person should enter the shelter of the categorical imperative, for if everyone does not do so, someone will surely be harmed.
And I want to discuss several aspects: 1- Here his decision will not affect others at all and there will not be a critical mass of anger that will cause harm.
(And not as theft from the state.) Is the answer to this that for Kant the commandment is not an outcome consideration, but an ontological one?
2- Apparently there is no harm to others here (except at most in the name of "the public" that one of them will die), does the order belong here? Or maybe it does because
That the SS is harming itself, but is this considered a moral decision?
Thank you very much!