What action do you take when an employee made a significant mistake?

I WILL FIRST TRY AND STOP THE FURTHER CONSEQUENCES MADE BY THAT MISTAKE. I WILL ALSO DO THE ROOT CAUSE ANALYSIS OF HOW THAT MISTAKE OCCURRED AND HOW IT CAN BE AVOIDED IN FUTURE.IF IT IS THE FIRST MISTAKE MADE BY THE EMPLOYEE I WILL GIVE HIM WARNING AND CORRECT THE SYSTEM TO AVOID FURTHER OCCURRENCE,IF THE MISTAKE IS INTENTIONAL THAN I WILL TAKE ACTION ACCORDING TO THE COMPANY POLICY