Bill Paxton used the same beer can throughout the entire filming of the movie because they could only find one Hamm's beer can like that from 1979. The sound of the can opening was done off stage.
Lion's Gate had wanted to change the title to "God's Hands" at one point, but Bill Paxton and the writer Brent Hanley convinced them not to do it.
Jeremy Sumpter, who was cast as younger brother Adam, originally auditioned for the role of Fenton.
In the end of the movie, the two boys that ride across the screen on scooters are Matthew O' Leary and Jeremy Sumpter - the same actors who play Fenton and Adam Meiks as youngsters.
Adam's jar held a millipede, not a centipede. Bill Paxton asked Matthew McConaughey what a good name would be and he answered "Curtis". Thus the millipede was 'Curtis'.
'Osama bin Laden' appears in the lower-right-hand corner of the FBI's Ten Most Wanted List featured toward the end of the movie.
The flashback sequences take place in the summer, but the movie was filmed in November and the breath of some of the actors is visible due to the cold temperature, most notably when Dad and the kids bring the first "demon" into the shed and turn on the light.
[SPOILER] In the original cut of the film, the crimes of the "demons" were shown when Dad first laid his hands on them. James Cameron, a friend of Bill Paxton, viewed this cut of the film and suggested Paxton wait to reveal the crimes until the end of the film.
The lengthy scene in the car with Matthew McConaughey and Powers Boothe was actually shot on a sound stage. Director of photography Bill Butler had crew members slighting shaking the car and moving lights and props to create the illusion that the car was moving through the night.