Fringe (Fox sci-fi thriller serial, 2008)

Episode 1.03
Opens with an RTS transit bus in 'Harbor Bus Lines' livery and fleet number 7031 en route:
Man with briefcase boards, puts on a respirator and releases a canister of gas as the bus is entering a tunnel, causing panic:
The passengers meet a sticky end and the rest of the episode is taken up with the FBI investigation:
Episode 4.10: Forced Perspective
Interior and exterior views of a Boston Transit Orion V: