Here's a fun question. If everything is unfolding according to God's plan, is murder wrong?

Before you answer, consider this. According to christianity, God knows everything that will unfold, and has already accounted for it. So literally everything that happens is part of his plan. Presumably, this includes murder and any other horror the human mind can conceive. So I ask again: In such a system, is murder wrong? And if so, does that mean God's plan is wrong?