*A few minutes earlier*
Two men armed with firearms arrived at the cave's entrance to swap guard duty shifts with the previous two.
[Random guard: "Huh? Where did they go?"]
[Second random guard: "Where are they? They were supposed to be on the watch."]
[Random guard: "This should be reported!"]
His partner nodded, and they both went inside to report to their supervisor.
They were both heading down the corridor to meet with their supervisors when one of them sensed something strange.
[Random guard: "Wait! Wasn't there supposed to be people here? Why hadn't we seen anyone on our way?"]
Even his companion felt it was strange that they didn't observe a single person everywhere, now that he mentioned it.
!Bang!!Bang!!Bang!
While they were both perplexed since they couldn't see anyone else except themselves, a loud boom reverberated throughout the corridor.
[Second random guard: "What was that?"]