Some questions I can think of (not sure if they will be willing or able to answer these but it's worth a shot!):
- Were any tire tracks or footprints found at the scene that could help identify a perpetrator?
- Do authorities have a POI/suspect in mind?
- How was the determination of arson made? Was there evidence an accelerant (such as gasoline or propane) was used?
- Given the condition of the cabin, were officers able to recover any physical evidence (such as DNA, fingerprints, or hair) that could be used to include/exclude suspects?
- Did police check cell tower records to see if any other devices were in the area at the time of the murders?
- Did Dave frequent any local establishments (i.e., bars, restaurants, gas stations, grocery stores, etc.) where he may have run into someone who wanted to cause harm to him?
- Where in the cabin was the body found (i.e., on the bed, inside the front door, etc.)?
- Was anyone staying in the summer cabin on the property at the time? Did Dave allow friends/family to stay there? Was there any evidence that someone had stayed in the summer cabin recently?