Paranormal Activity
(2009)

Micah and Katie (like Blair Witch Project, the real names of the actors) are being haunted by a demon that has been attracted to Katie ever since she was eight.

Despite being warned by a psychic not to toy with it, Micah provokes the demon throughout the course of the film, resulting in the disturbances becoming more and more violent.

After Katie gets dragged down the hall and bit by the demon, Micah finally decides that it is time to leave the house.  However, when he is ready to go, Katie is in a comatose state and tightly gripping a cross in her hand (causing it bleed).  She then goes into bed and says that she does not want to leave anymore and that she thinks things will get better (though it's obvious something's not right with her).

During the final night, Katie rises from her bed and stares at Micah for a few hours before leaving the room.  Micah is awoken by the sounds of Katie screaming and he runs towards her.  A few minutes later, Micah is thrown towards the camera and Katie is seen standing over him.  Katie then walks towards the camera before suddenly lunging towards it (revealing she was possessed by the demon).

Intertitles state the Micah's body was found soon after and Katie was never heard from again.

ALTERNATE ENDING: (Screener version only)
Katie rises from her bed and stares at Micah for a few hours before leaving the room.  Micah is awoken by the sounds of Katie screaming and he runs towards her.  A few minutes later, he screams and all becomes quiet till Katies climbs up the stairs to the bedroom alone with a blood soaked shirt and a knife ~possibly after stabbing him after being possessed... she sits on the floor and rocks back and forth all night.. phone rings early in the morning till the following night as she is still rolled into a ball rocking back and forth. Police come in and announce there presence with guns drawn. Katie gets up carring a knife and starts walking toward them and after failed attempts of getting her to drop the knife Police shoot her and kill Katie. Officers request assistance after altercation.
 
Movie ends with (in loving memory of Micah and Katie) with photo of both.

Thanks Sean and thanks Cesar for the alternate ending!