1. God timelessly believes K and is infallible.
2. Nobody now can do anything about the fact that God timelessly believes K and is infallible.
3. Nobody can do anything about the fact that if God timelessly believes K and is infallible, then A will kill B on Saturday (what is next Saturday to us).
4. So nobody now can do anything about the fact that A will kill B on Saturday (what is next Saturday to us).
5. So A will not kill B freely.

From Linda Zagzebski, Philosophy of Religion, quoted in W. Jay Wood, God, 2011.