When the troopers are leaving the base, two of them go into the airlock first with Aliss, but the airlock's digital readout shows four occupants.
When their equipment detects a heartbeat on the ship, the soldier Shaya yells "Weapons up!" Everyone who is armed, including herself, already has their weapon drawn and "up". Seconds later, though nothing about the situation has changed, the armed soldiers are back to relaxed weapon status again.