For psychological condition, see Panic attack
Panic is a sudden fear which dominates or replaces thinking and often affects groups of people or animals. Panics typically occur in disaster situations, or violent situations (such as robbery, home invasion, a shooting rampage, etc.) which may endanger the overall health of the affected group. The word panic derives from the name of the Greek god Pan, who was said to have the ability to cause extreme, irrational fear, especially in lonely or open places.Prehistoric man used mass panic as a technique when hunting animals, especially ruminants. Herds reacting to unusually strong sounds or unfamiliar visual effects were directed towards cliffs, where they eventually jumped to their deaths when cornered.Humans are also vulnerable to panic and it is often considered infectious, in the sense one person's panic may easily spread to other people nearby and soon the entire group acts irrational, but people also have the ability to prevent and/or
Source:
http://en.wikipedia.org/wiki/Panic