Let me run this past you guys.
Given that prescriptions and drugs from other burglarized homes were found in the teens car; that's what they were obviously after. And they both went straight to his basement...
The home owner and his relatives claim his house had been broken into multiple times before (8-10), but he only reported one. The only one he did report had stolen prescriptions and a firearm. I'm guessing the only reason he reported the one is because a firearm registered to him was stolen.
Based on that, and the fact that he waited an entire day to call police, leads me to suspect he probably had a quantity of illegal plants in his basement he needed to clear before getting authorities involved.
I can't see any other reason for executions, or waiting to phone the police. Maybe I watch too much TV, but I think were missing a chunk of the story.