Agreed, it could be just a nut case. But the behavior of the shooter following the incident is textbook. If I'm wrong I'll be surprised. Not maligning the victim, just looking at the known facts and forming an opinion.
Forming an opinion. My opinion is, you don't know squat so you should keep your opinions to yourself when something like this happens.
If you're wrong you'll be surprised? Big deal, what will you do then, go apologize to his widow for maligning the man?
