Criminal Minds2005

Dr. Spencer Reid:
You know, the fact is, this is an experienced sniper who can account for timing. After the first shot, no one moves. People are puzzled. Everyone's reaction is to look for a source of the sound. After the second shot, it takes the average person one and a half seconds to cognitively process that they're in a potentially life-threatening situation. It takes another .7 seconds for a physical response to kick in. By which time the third shot has already been fired.

Jennifer Jareau:
So the UnSub wanted victim number three.

Alex Blake:
Well, anyone after number three had a chance of getting away, and the UnSub wouldn't have taken that risk.