Is it possible he didn't park in the driveway....and used Walnut Park Access roads instead....also in the dark is it possible he wasn't aware of how close to a house he was? Assuming if he had gotten to that spot through the park.
Morgan's remains were in a spot that would have been tough to drive right too, meaning she would have had to have been carried...JLM is a big guy, if he could have carried Morgan, he could have carried HG too. So maybe it was the park he entered and chose...not neccasrily that house?
MH had many broken bones. Although graphic, I am under the impression MH was just ran over by the car. HG's skeletal remains were intact