Summary[]
In 1967, Mandy slaughtered her entire family, out of her hatred for Bill and his antics. Bill was beheaded, Kyle and Jeremiah were shot to death, Antoinette and Jane were both hypnotized to carry on Mandy's work, and Marina shot Mandy to near-death with an assault rifle, after losing her whole family.
This kickstarted the entire series of events that followed, and is why everything that happens in the future, does. Because Antoinette and Jane are now evil.