Boston Marathon Manhunt (2) - S2.E2

In the tense hours following the bombings, Sergeant John MacLellan heads out on his night shift. That same evening, an MIT police officer is murdered by two attackers. No one knows yet that the cop killers and the bombers are one and the same, and Sgt. MacLellan comes face to face with the perpetrators. The shootout that ensues leads to a citywide manhunt.