Criminal Minds: Suspect Behavior Season 1 Episode 6
The episode opened with a family out to take pictures by a lake. The daughter told the mother she saw someone following them. As the father went back to his car to get a new battery for his camera a man knocks him out and then lynches him in front of a girl.
Cooper and his team come in and are on the track of the killer quickly. Cooper and his team figure out which way he was going and are on the trail of who they think might be the next victim and are too late and find him hanging from the edge of tunnel entrance.
Cooper and the team figured out that the girl he is killing for is actually dead and the killer is much more mentally unstable than they thought. As the team began to unravel the clues they figured out that the killer is taking the corpse of his dead sister to DC to confront their father who left them years before.
Cooper and his team got to the house of the father before the killer could lynch him too. The team managed to prevent the killer from killing the father or himself.