From Within (2008)

In a small Maryland town, the suicide of an outcast teenager triggers a string of violent suicides. These suicides seem to stem from a curse which spreads when any person, who witnesses the suicide, is possessed by an evil force that appears as the person's doppelganger that only they can see.

A young teenager, named Lindsey, thinks there is a connection of the events to Aidan, the outcast brother of the first suicide case. But Lindsay must race against the clock when she witnesses her mother fall victim, and must try to find a way to stop the curse before it kills her too. Meanwhile the God-fearing townspeople, led by a fanatic preacher with a connection to the events also, form a vigilante group to take the law in their own hands.