Not enough info (as usual) to make a definitive call. BUT, taking the news story as writ (always dangerous) it sure sounds like a questionable shoot. The guy was unarmed, but that doesn't meen he wasn't dangerous. What we don't know is how he approached the cop, what the cop said, what the dead guy might have said back, etc. It certainly though seems like a potentially better application for a baton or perhaps a Taser rather than a double tap from an AR-15.
Oh, and BTW, if I was on the jury I'd not give any weight to the statement "Cougan, as a deputy, was shown preference during the investigation by not being required to give a statement until after consulting with an attorney."