Defend Keyes while he overrides the lockdown | Mission 1: Distress A: CM Guide

Now it's time for a defensive task. Stand behind the barricade and take a moment to locate some ammo and armor (if you need them). When the battle starts, focus mainly on those Xenos that will appear by the hatch. Depending on preferences, you can use the pulse rifle or (if you don't have ammo for the grenade launcher) the shotgun.

While fighting, keep in mind that in case you find yourself directly in front of a Xenomorph, you can perform a melee attack: hit it with the butt of your gun.