The following are a collection of articles, some neighbor to neighbor, others nation to nation.
Some times people have stood by and done nothing as others were hurt or killed.
Other times, people have intervened, even risking their own lives.
Stories like these beg the question:
Should people/nations intervene in others' affairs?
If so, when?
Others who watched
Some other clues as to why foreign guards may not help are found it this article
Others who risked their lives