CoD: Black Ops Harpoon....?

I'm a little into the game with the Russian prisoners revolting. I'm at the point where you have to run up the stairs and grab a harpoon and take down the helicopter. I'm chopped apart before I can even get ground. The walk thru's just say "take cover". I CANNOT run back inside the building because the asshole is blocking the door and I'm killed within 3-4 seconds. There's NOTHING to crouch behind nor can I jump. I'm going to have nightmares over "MASON, GRAB THE HARPOON! CHOOSE YOUR MOMENT!! NOOOOOO!!!" Please help....