I also think MS was the shooter. I think the hatred everyone has for DM makes people want it to be him, but I think the evidence points to MS being the idiot that pulled the trigger. I believed the best friend who said Mark showed him a YouTube video of the gun MS wanted but that FM ended up with, and I believe the gun used in the murder was the lesser one MS got and that ended up in the toolbox. I think at some point after the murder DM got the gun away from MS for his own safety and perhaps that of others, and that DM was planning to hold onto that gun as insurance, so that he cold prove it had MS's fingerprints on the Griffey and possibly the remaining bullets. I think that's why he gave the gun to a friend he could trust and not to MS, who he had also seen that day.
I think that if DM had planned on a murder that night, that he would have worn at least a hat or baggy clothes or something to disguise himself at least a little, like MS did. I believe SB did not see DM wearing a purse because he didn't have it on him and that without it, he had no place to conceal a weapon, like MS did.
I beleve MM when she said MS was violent and not always nice to her, and I believe if DM was also abusive, it would have been brought up by at least one of the girlfriends. I believe that when MS repeatedly told everyone that he had f'ed up, that he was blurting out the truth, that he did f up everything and go completely off the plan. I believe that when DM says he was cleaning up MS's mess, that he genuinely complaining, unlike the weird third person descriptions where he seems to be working on how he will spin his story. I also think that when people are telling how they will spin their story, as he was doing, that there are usually elements of truth woven in to strengthen the story.
And I believe that any dog owner would known ahead of time that a dog could be a possibly unpredictable but definitely difficult addition to a violent crime, and that if killing was DM's plan, DM never would have brought a pet along. In fact, the pre-planing was so lax I still can't imagine it being anything other than a hastily made afterthought, as if DM, the planner, were instead cleaning up Mark's mess. I think it was a mission to scope it out that went terrible wrong, and that as several witnesses have testified, that Mark is the one who f'ed up, and he knew it, and confessed it in that fashion to his close friends. So many reasons why I think it was MS, I can't fit them all in here.