I wonder if this might be the scenario. The man got fired that day, we know that. Maybe he made some threats and his employers called the police and asked them to be on the lookout. Police being proactive stopped him on the pretense of a signaling violation (not often done). Shooter had in fact armed himself and was planning a revenge attack on his boss. When the cop stopped him he said "I've had enough" and started this rampage.
Sounds about right.
That is just about the way I have it figured too! I drive that stretch of road daily and you seldom see anyone pulled over, mostly because the troopers are too busy working crashes.
My biggest fear is when I die my wife will sell my guns for what I told her they cost....
