It takes training and skill to shoot two people in the head. Doesn't sound like it occurred up close. I wonder what his background was. The videos of him show that he has difficulty operating a pen, let alone a knife and a rifle.
Seems like he was under the influence in the body cam footage where he's getting the citation. Maybe that's just how he is. In either case, the guy is obviously not well, or a very good actor. From reports of his neighbors, I would tend to believe the former.
And so much that isn't known at this point and we may never know. Like mentioned above, rational folks tend to wait until more details and facts are known before jumping to conclusions.