Panic
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 irrationally, but people also have the ability to prevent and/or control their own and other's panic by disciplined thinking or training (such as disaster drills). Architects and city planners try to accommodate the symptoms of panic, such as herd behavior, during design and planning, often using simulations to determine the best way to lead people to a safe exit and prevent congestion (stampedes). The most effective methods are often nonintuitive. A tall column, approximately 1 ft (300 mm) in diameter, placed in front of the door exit at a precisely calculated distance, may speed up the evacuation of a large room by up to 30%, as the obstacle divides the congestion well ahead of the choke point.
In sociology, precipitate and irrational actions of a group are often referred to as panics, as for example "sex panic", "stock market panic".  (See hysteria.)  Panic is usually understood to mean active, but senseless behaviour (e.g. trying to flee in a random direction or suddenly attacking others without consideration), while hysteria often carries a more passive notion (as in crying uncontrollably). An influential theoretical treatment of panic by a sociologist is found in Neil J. Smelser's, Theory of Collective Behavior.
The science of panic management has found important practical applications in the armed forces and emergency services of the world.
Many highly publicized cases of deadly panic occurred during massive public events.
The layout of Mecca was extensively redesigned by Saudi authorities in an attempt to eliminate frequent stampedes, which kill an average of 250 pilgrims every year.  
Football stadiums have seen deadly crowd rushes and stampedes, such as at Hillsborough stadium in Sheffield, England, in 1989. This led to controlled entry gates and stricter rules by the end of the 1980s to regulate seating arrangements.

# Etymology
"Panic" comes from Greek panikon, "pertaining to Pan." Pan is the god of woods and fields who was the source of mysterious sounds that caused contagious, groundless fear in herds and crowds, or in people in lonely spots.

# Panic and the law
Most jurisdictions limit the freedom of speech in order to deter people from creating potentially dangerous panic situations, especially a false alarm (the classic example is shouting "Fire!" in a crowded theatre when in fact nothing is burning).
Some criminal defendants attempt to evade or reduce the severity of their conviction by claiming their violence was induced by a sense of panic.  Certain jurisdiction may limit punishment in case one's actions for self-defense were excessively powerful because of panic reaction.
Panic experienced by air travellers during the last minutes of their lives aboard crashing commercial flights has been the basis of several multi-million dollar lawsuits brought against airlines, based on the legal concept of emotional suffering.