On top of the car of the suspects, it says "Broken Arrow"
Broken Arrow
Broken Arrow refers to an accidental event that involves nuclear weapons, warheads or components, but which does not create the risk of nuclear war. These include:
Accidental or unexplained nuclear detonation.
Non-nuclear detonation or burning of a nuclear weapon.
Radioactive contamination.
Loss in transit of nuclear asset with or without its carrying vehicle.
Jettisoning of a nuclear weapon or nuclear component.
Public hazard, actual or implied.
link to en.wikipedia.org (secure)
Broken arrow is also a Military command when an american unit has been over run by the enemy!