Honestly guys the more news that comes out about this, the more I think this was just an elaborate suicide.
The way people speak about him, he was an odd rather paranoid recluse, friendly but lonely, as his neighbors said he never had guests over. It seems he wanted to end his life, but he also desperately wanted people to remember him, but didn't want to kill anyone for that infamy. When looking through that lens it makes sense. He rigged the RV to explode, drove to a main street in Tennessee, called the police with a fake claim of shots being fired as to get them to the RV, play the tape so they would start evacuating and keep people from getting close, then boom, end it all. If he simply killed himself with a shotgun in the mouth, only his neighbors might remember him. If he hung himself in the middle of Tennessee, maybe only the city would remember him. Blow up a street on Christmas day though? That's nationwide news.
He got what he wanted.