Serious SPOILER ALERT! Before Steven Spielberg suggested the finale you see on screen, director Peli considered many other endings. Check out these three.
The original ending? Police find Micah’s body — and Katie with a knife. When a door slams, a startled cop shoots her dead. (You can see this on YouTube: Search for ”Paranormal Activity original ending.”)
Katie returns to the bedroom after the melee downstairs. She grins wickedly at the camera — and then slits her own throat. The demon then leaves her body, and Katie falls lifelessly to the floor.
A possessed Katie corners Micah and bludgeons him with his precious camera, while viewers watch from the camera’s POV. This version of the ending was so complicated that Peli never actually shot it.