To me some things just don't add up. If it was DG and he used the green truck, surely there would be some trace of blood, hair, finger prints etc of the victims. This alone would likely be grounds for arrest even without the bodies.
If indeed it was him and we presume the worst case scenario I don't see how there could have been a violent struggle, dragging bodies, transportation to another site, dumping/securing the victims, cleaning vehicle spotless, scrubbing the driveway all in about an 8 hour period (before daylight) without being seen by anyone.