Mostly used at the end of a sentence to hint something without having to actually spell it out for the reader, whilst adding a solemn, dire, suggestive or perhaps a cheeky tone for either comical or epic purposes.
Example 1:
-During a zombie apocalypse-
Badass 1: u don't have to do this alone...
Badass 2: yes I do, u must take care of the rest. I won't be coming back. if the zombies break through the barrier..