An awesome game! I think I have part of the story figured out. Julie was ejected from an airlock. Andy was killed by Butler because he thought he was the monster (explaining why he had multiple stab wounds. Butler was killed by the alien (I assume since he didn't have any visible marks on him). One thing I'm not sure of is whether I was controlling Captain robert or the alien? From the last note I read of him, he was on his way to the escape pod, meaning he had the escape pod key. Perhaps the alien locked him in the storage room (which is why you can't find the escape pod key). I could be very far off base with this idea, but it is just a thought.
The only reason I didn't give you a full five stars is because I wanted to know who was behind the storage room door. I know ending it this way forces us to make our own conclusions, but I really wish I knew what you had in mind for what was behind the door.