S06:E04 - In the Line of Fire

Bombers, snipers, spree killers: some people don't care who they kill, they just want to hurt innocent people. These killers are the hardest to catch because they have no connection with their victims, who are just in the wrong place at the wrong time. But even random bloodshed leaves traces at the scene that can direct an investigation and stop the killer before he can strike again.