I'm playing Shadowgun and am at Level 3. I'm running through a cave and arrive a a location to pick-up a key-card. After the key-card is picked-up some cave door opens and the "Driller" appears. I yell "Oh Hell!!!" None of my weapons work to stop the driller, I try to run away from the driller, but always get killed. What do I need to do to overcome the Driller?