Didn't DE already buy a shovel and cleaning supplies prior to picking her up? Authorities already said DE and NK have been plotting this murder for a while.
Yes, DE was a predator. He wasn't some guy involved in a relationship looking to go on a date. He was a sick sociopath who stalked a young girl into a manipulative, controlling sexual relationship for the purpose of killing her.
While LE only has evidence that he began planning the murder with NK in January, IMO, he had murder or something similar. on his mind from the time he began the relationship with NL.