A strange event

Elaine is a Muggle, No-Maj.. however you call it. So how is she using the killing curse to kill people?

When Newt, Tina, Jacob and Queenie are sent to find out more, they discover that Elaine is controlled by someone. She puts everyone in danger by simply existing.

Who is doing this?

And why?

This story is a continuation after "Fantastic Beasts and Where to Find them", inspired by "Crimes of Grindelwald."

(sorry I suck at descriptions.)