The autumn morning is sunny with heavy crowds using the several subway trains. It is a perfect day for shopping at the mall and other shopping areas around the city. As passengers are boarding a subway there's an explosion that rips the on-coming train apart. Panic gets over most of the crowd. Various minutes there's another explosion in the station. More panic.A security guard quickly dials 9-1-1: "I'm calling from the Waldorf Station. We've just had an explosion in station and one on a train." Everybody's screaming. I don't know how many are injured... People are injured and some appear to be quite serious! "Based on the over description, what type of disaster do you believe happened at this instance?