The weeks ahead will shed a lot of light on this issue, however as it stands now there should be little argument that this man seriously messed up. The only question is whether the mess up was due a) to his actions following a legitimate shooting as he defended himself; or b) an unjustified 'hotheaded' shooting that equals major jailtime. It is either or, and in both cases Dunn messed up.
I am pasting a link to an article by Massad Ayoob on the three main mistakes people make after a JUSTIFIED shooting. It would seem Dunn read the article and decided to do exactly as it said - in the inverse.
http://www.armedcitizensnetwork.org/3-most-common-post-shooting-errors