I feel really stupid right now...
I'm at the gas station, giving Nantz cover. Problem is, halfway through, the alien ship shows up, and it keeps machine-gunning me to death. I can't give Nantz cover without exposing myself to the ship. Am I supposed to run to ground level or something? Am I too slow in taking out the aliens on the ground? What the hell is going on? It's driving me insane, because I know I should be able to get past it, and obviously others have, because they've beaten the game. I've beaten all the Half-Life games, there's no way this $10 hour-long game should be defeating me!