Having just found Armstrong's body, Lombard and Vera realize that they are the only two people on the island.  Everyone else has been murdered.  Vera knows that she isn't the murderer, so she thinks it is Lombard.  Lombard knows he isn't the murderer, so he thinks it is Vera. 

Vera convinces Lombard to help her carry Armstrong's body over the high water line to get him out of the reach of the sea.  It proves to be a hard task, and while they are doing that, Vera leans against Lombard in a gesture of help and steals the gun out of his pocket.

Vera aims the gun at Lombard. Realizing the end of his life is near ---- Lombard tries to talk to her and lull her into a false security.  Suddenly he makes a move to take the gun away from Vera.  She shoots him through the heart.