Let’s Find Out Who Did This!
One of the problems in problem solving in organizations is that people aren’t seeking the cause of the problem, they’re seeking blame.
The problem with this is that, whether this is actually the “guilty” party found or not, penalizing that person or removing that person usually doesn’t solve the problem. You can’t remove the adverse effects of a problem until you remove its cause. A clerk making a poor decision on the priority of a delivery perhaps should have used better judgment, but if there are no clear criteria for setting delivery priority, that cause will remain unless corrected, no matter what you do to the clerk.