I think the issue might be "necessary, but not sufficient, conditions". In many things, a number of elements are necessary to satisfy a requirement. Each one of those things is a necessary, but not sufficient, condition. So in this case, if the cheerleader was killed by Syler, then the catastrophic result became inevitable -- inescapable. However, there is still more work left to be done to avoid the catastrophe.

Oh, I didn't even think about that.