At the end of the movie, we see that it was James Costa aka Martin Asher who is the real killer. But by that time, its too late as he escapes, fucking Scott & taking another life. Scott is terminated from her service at the FBI for her conduct. In the last scene, few months later, we see Scott, pregnant, coming from a store to a secluded house living all alone. Asher/Costa arrives there & abuses & threatens her to start fresh with him. Finally he loses his mind & stabs Scott in her belly, but Scott pulls back the scissors & stabs his chest revealing that this whole thing was staged(she isn't pregnant) to nab Costa/Asher. Scott then tells Leclair about their success.
My question is if this whole sacking of Scott & her living secluded, pregnant, was a set up to catch Asher/Costa, as he would come to her, How can Scott kill him? She is bound by the law, this whole thing was a setup by the authorities. She expected Asher/Costa to abuse her when he came & possibly attempt to kill her, but how can she kill him & get away with the law. He is not a convicted murderer. He hasn't undergone a trial.
Also, Leclair must have known that Asher/Costa would try to harm her, so why didn't he have an arrangement to catch the killer alive. Is this setup & most importantly, the killing part, legally justified?