Leon didn't know she was Carla and carla was working for neo umbrella and those people in the helicopter shot her in the chest and she went down as a bio monster and ada Wong ended her
I think Carla was planning all this to tracking down Simmons and ada Wong was tracking carLa and Simmons and ada Wong was using her grappling gun outside the building and Simmons pushes leon down on the ledge and ada Wong you can't always want you Simmons and she stabs him with a arrow in the side and saids no