Verified answer

They are being haunted by a demon that has been following Katie since she was a child.

The guy (Micah) provokes the demon, the demon gets ticked off, and in the end posses Katie, then while under possession, kills Micah.

In my opinion it wasn't a conventional movie, but how would you call it, a

mock documentary / reality style film which proceeds to show supernatural

events going on in a suburban house, in a low-budget, surveillance video style.

Similar to movies like "Quarantine" or "The Blair Witch Project"