This thread is more like a half dozen different serial killer movies at one time.
For all we know the shooter is reading this thread right now, and getting off on it. This may be exactly the kind of attention they crave.
It seems to me that the above pharse is sarcastic. It is a taunt aimed at the police/government officials. The odd phrasing of this statement only makes sense if it is sarcasm. If I was to say to a police officer who stopped me for a traffic infraction "Well Mr. Policeman I don't think the light was red". What would be the normal reaction of a police officer. It would tick him off. He would think I was being sarcastic and belittling him. I think the killer is being sarcastic and belittling the police. I do not believe that the killer thinks that he is god or even thinks he is divinely inspired. He is just being a smart mouth. He probably used the death card because he thought it looked cool.
I am leaning to a domestic nut/nuts rather than terrorists now. However, I am not convinced that the killer did not plant the card and the shell casing as a red herring. Planting a card and sending the police in circles would probably amuse a terrorist as well.
The other interesting bit to come out is the possible first shooting on the 14th of September. This could be a proof of concept shooting. The killer was probably disappointed that his act was not more widely recognized. He spent a few weeks planning his next spree killing. Now that he has got everyones attention he can slow down his pace again. I still think he will shoot again before the week is out.