I have another theory. It is one basic goal of domestic terrorism to put a wedge between the government and the people, and create distrust. More or less the marxist terrorist MO, but effective nonetheless.
Thus, the shooter deliberately bypasses shots at cops, leaves communications for the cops that he knows will not be completely shared with the public, and the media speculation and little leaks just play it up all the better.
In the end, you have a case that seems unsolveable to the ordinary citizen, they have reason to distrust the police (and LE in general), and they see themselves as separated from justice; mere targets for the amusement of others.
This is effective terrorism! Consider what is going to be going through people's minds across the country on Halloween. Not to mention the nutjobs that will emulate this, or individuals cells that will get the idea that they should activate. Who knows, maybe capitalism has rubbed off on the Hamas-in-the-US set and they are making bids for jihadinasty money from saddam?