 SPOILER: According to the director, the screenplay version of the  film had the entire movie from Maries version of events. You didnt  find out she was the killer until the end of the film after Marie  defeats the killer and rescues Alex, when it would cut back to the  Hospital Room and you see Marie in handcuffs. A police officer would  roll in a TV and show Marie the video of her killing the gas station  attendant and ask if she wanted to change her story. The real  version of events was meant to be another movie entirely. However,  when the writers presented the script to Luc Besson, he convinced  them to change the ending to include the last reel of the film  revealing Marie as the killer, instead of the last five minutes.