Attack the problem, not the person. 

Often, an incident comes from a poor procedure or lack of clarity. 

At Disney, we dig all the way down and find out why this happened, not focus on blaming the person. Even when there was an accident, we didn't focus on the person. We wanted to know what caused the accident. What really happened?

When you blame the person you rarely solve the problem. 

If you want to find the real problem, be a detective. 

Talk to the person. Visit the scene. Review your policies. Talk to other team members to see if they think there is a policy or procedure that lead to the incident. 

In time, you will create an environment where people know you will attack the problem or process and not the person. Then people will be more willing to tell you upfront what caused a problem. 

You may find the problem is clarity in training or policies. Uncovering this will allow you to fix the root of the problem.