CLEVELAND -- Contagious shooting is a sociological phenomenon usually connected to police or military in high stress situations where one starts firing and others follow.

It's important to note that there is no scientific evidence to prove this actually happens but it's a theory many believe has some basis.

There are several examples of cases where police fired multiple rounds and sometimes injured bystanders. Is it possible that the actions of one trigger the rest?

"Mob mentality theory might account for that behavior but intervening variables such as specific training that military or police have, we assume,might countervene mob mentality and there's been no science to support whether mob mentality could be applied to shooting contagion,"says Dr. Jeffrey Janata Ph.D. of University Hospitals.

Police officers put their lives on the line every day and most civilians have no concept of the dangers officers face. They go through intense training including firing together on a firing range.

Law Enforcement expert, Pete Eliadis, suggested another theory in a 2009 article on Officer.com. Conditioned shooting, or finding support in hearing additional gunshots may prompt others to fire. He also suggests that type of training perhaps should be modified.

Other experts believe it may be a reaction to sudden fear. All thirteen Cleveland police officers said they feared for their lives that night.