A police officer answers questions on Ferguson ...

Link here

The whole article is great.  Here's an excerpt:

Shooting events are over far faster than most people think. According to a scientifically-validated study on reaction times, the time from a threat event to recognition of the threat (the decision making process) is 31/100 second. The mechanical action of pulling the trigger is as fast as 6/100 of a second. 

For those who aren't anti-police but are curious about some issues claimed in the Ferguson case, this is great.