Aliens: The return

A while later you reach the medlab. You are about to enter when your radio buzzs. You pick it up to hear Coporal Davis's panicking voice. "We're under attack!" he shouts "theres too many of them! They're coming out of the walls!!! Back up needed! Please we need help, oh shi...! AARRGGGG!!!". The radio goes dead. You look at your marines. "We need to help them!" said Private Roberts. "I know" you reply "we'll head through the medlab towards where they went". As you enter the medlab you notice a strange substance dripping from one of the holes. You look up. Are you carrying a pistol or a pulse rifle?