The mission should be aborted.
Aside of the fact that this hypothetical case is highly unlikely.
you've heard of the SAS, and missions like BRAVO-TWO-ZERO, right?
Or maybe deep-cover operations carried out by MI5/6/The Police - all of which cannot be simply "called off" like turning a game off an on.
I'm sorry dude - but you obviously have no idea why most secret military or civilian ops are secret, and seem to genuinely believe that the sole purpose is to cover up war crimes. Matey, I've got news for you - Government is FAR too incompetent to cover-up _anything_ for any length of time.