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.