Thanks a lot for playing my friend, I always appreciate your videos and feedback. I have you say, you are the only one, who asked that question and to be honest, I don't actually know, more like I can't tell. The story is strictly linear and tells the tragic story of both sisters. Now, you hear the gunshot, and the game ends, but was it an actual event that happened or was it a dream in her mind? - Not a bad theory, but again, I can't tell, because in a way it is up to you to interpret the ending, like a "glass half full, half empty" situation.
Best of luck and thanks for the topic. Cheers!