Outside of any scripted, story related elements, is it possible to actually kill the alien at any point in the game or must you wait until the end. Assuming the alien does actually die in the game?
There is only one alien in the game. Killing it would take the main gameplay element of the game away. There are various weapons that you can use to stun and repel the alien, but there is nothing that you can use to kill it. You must sneak and use stealth to survive.
there are other enemies in the game to kill, but the alien can’t be killed.