It is not even close to blaming the hurricane on the butterfly.

While it should not be possible for such a prank call to lead to a lethal outcome, it currently is entirely possible and realistic for such an outcome to occur in our society today. The perpetrator knew that was a very probable outcome, and used that knowledge to intentionally instigate such a scenario in order to achieve that outcome.

Just because he didn't pull the trigger doesn't mean he doesn't share any blame.

The world is not the perfect, logical, orderly fantasy-land you seem to think it is.