How does Edmund take advantage of Simon Tucks in the book, Afterlife: A Novel?

Simon Tucks is a terrorist on the run from the FBI. He is a sniper who killed 18 people so far, including Emily Watkins and Will Brody. Simon also ends up killing Claire.

Simon is a vulnerable person who is taken advantage of by Edmund, who whispers in his ear to make him do bad things. Simon of course does not realize that this is happening and simply thinks that this voice is another part of himself, which he takes to calling his True Self.