jesus man, don't sneeze!

A Contagious shooting or "Mass reflexive response" is "gunfire that spreads among officers who believe that they, or their colleagues, are facing a threat. It spreads like germs, like laughter, or fear." ^[1]

Incidents

• 2006 Five officers fired 50 rounds at Sean Bell who was leaving his bachelor party in New York, including 31 by one detective^[2]
• 2006 Three officers fired 26 shots at a pit bull that had bitten a chunk out of an officer’s leg in the Bronx, New York in July^[3]
• 2005 Eight officers fired 43 shots at Brian Allen, an armed man, in Queens, New York killing him^[4]
• 1999 Five officers fired 50 rounds at Amadou Diallo in the Bronx, New York on February 4, 1999
• 1998 New Jersey State Police fired 11 shots at Daniel Reyes and three other basketball players in their car in April ^[5]

-http://en.wikipedia.org/wiki/Contagious_shooting

I think the simple explanation for this is that shooting at people is a lot of fun and you're not normally allowed to.