The base had two 'military' forces – the police and the army.
Similar to before the apocalypse, the police were responsible for internal security including patrolling the base and catching criminals.
On the other hand, the army was responsible for dealing with external threats and their job included manning the base walls, collecting supplies, clearing the surrounding areas, and expanding the base perimeter amongst other tasks.
At this time, it was naturally more appropriate to contact the police than the army.
"Has someone contacted the police?"
"Someone seems to have gone. Let's just wait."
"But I wonder if this notice is true…"
"I think it's true."
"Why?"
"Would someone be so stupid as to tell a lie that would be revealed when the door is opened?"
"You are right but…, they didn't leave an actual name. What can we do to them even if we discover they lied?"
"Aren't all of you ignoring the important matter?"
"What important matter? What do you mean?"
