In Alexandria, Va., Nancy Dunning, Ronald Kirby and Ruthanne Lodato are all fatally shot in broad daylight by a gunman knocking at the front door; detectives attempt to use security footage to track down the killer before they strike again.

On March 27, 2015, Tierra Hall says goodbye to her mother for the last time. 24 hours later, the teenager's dead body is discovered outside an abandoned house. With few clues on the scene, can surveillance footage help police crack this brutal mystery?