I've wondered, all through this, if they tried to make it appear that KR did this, or, with KR being different, they were trying for the drug deal gone bad, angle, and KR was the head honcho. DS, while I think he's a sketchy fella, I think that he came off as being more-so sketchy, because he'd tried to pull a fast one over on his wife that night, and had claimed to be at KR's. He wasn't, he was with a female friend. When they asked him to go check on KR, he knew his cousin was likely dead, and he knew he was going to look suspicious, in addition to his marriage was likely going to be over too (and it was), in addition, it appears that the Rs and Ms have kinda ostracized him. He may have taken something, thinking, in his eyes, that LE is going to take it anyway, so I'll just take it before they do.