Perhaps unintended, the death of Rachel's older sister Zelda happens on Passover, but this coincidence goes unremarked. The unnamed thing in the burial grounds is implied to be the thing that caused Zelda and Gage's death and Louis remarks that thing in the burial grounds is an old god, existing long before the Christian God, perhaps the nastier Old Testament God.
In the book, the entity is heavily implied to be the Wendigo.
Actually, there is this bit in Insomnia where the main characters find Gage's shoe in the bad guy's lair. The bad guy collects trophies from his victims, so...
Atropos is the servant of the Random. He's not the one who causes senseless deaths directly, just the agent that facilitates them by cutting the threads of the victims.