Continuity mistake: In the shot where Holly is done injecting Anna with the syringe and stands up to shoot at Detective Loki, the syringe and two "medicine/poison" bottles are all close together next to Anna's hair. Next three shots showing the room far out with Holly getting shot and killed has the two bottles next to the edge of the rug and very far from Anna's hair, as well as the syringe which is slightly closer, but far away. The next shot of Loki picking up Anna has the syringe and bottles in their original position next to Anna's hair.
Continuity mistake: In the final scene where detective Loki shoots Holly before injecting the poison in Anna's arm, her legs change posture in two different shots.
Continuity mistake: When Detective Loki is speaking with Keller shortly after leaving his home, Detective Loki can be seen chewing on a toothpick while sitting in his squad car, which disappears in the next shot.
Chosen answer: In the film it is just a coincidence. However, the snakes tie into the rest of the religious and mythological imagery present in the film.
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