‘He who amongst you sees something abominable should modify it with the help of his hand;
and if he has not strength enough to do that, then he should do it with his tongue;
and if he has not strength enough to do even that, then he should (at least abhor it) from his heart; and that is the least of faith.”
Sahih Muslim Hadith 79 Narrated by Abu Sa’d al Khudri
Our remorse should come for the crime itself and then for our own ineffectiveness to stop the crime. Sometimes not being involved is complicit if one does not speak out against injustices.