This just sounds more and more like a case of road rage taken to a wrong, disastrous level.
Bingo! Sounds to me like a 17 year veteran lost his cool and made the wrong move. If this woulda been two civilians the shooter would be locked up by now.
Edit: Dont get me wrong I hold the utmost respect for law enforcement officers (Im actually going to start school for criminal justice here in a year or two). But wrong is wrong doesnt matter if its a cop, the pope, or president obama, the law isnt and shouldnt be different for anyone.