While this does make for great movie viewing, it is actually not a true reflection on how humans would respond to such an event.
The technical term is Emergence, and it relates to the way complex systems arise from combinations of simpler systems interacting. For instance, physical objects can be viewed as the emergence from molecules and atoms, while these can be viewed as emergence from subatomic particles.
In human terms, the concept of emergence is manifested by the spontaneous creation of order when people are left to regulate themselves. This is in stark contrast to the unmitigated chaos the movies would have you believe, but has been observed and studied as far back as the 4th century BC.
A simple example of human emergence in every day life is the humble traffic circle. Here one has numerous small systems (cars) all interacting in a manner beneficial to the collective system (the traffic flow).
