Paramount Pictures released a new teaser trailer to horror thriller film “Paranormal Activity 3” today. This new sneak-peek footage of a prequel tells the back-story to “Paranormal Activity” trilogy heroine Katie and her sister’s experiences with the demon that’s been plaguing their family for generations which is once again told through the perspective of cameras. The third installment “Paranormal Activity 3” opens in theaters October 21, 2011. Watch the new trailer below: