I have met a few people in my life who have taught me (subconsciously) how to keep a cool head in high stress situations. I've been in the shoes of both sides.
I've witnessed people losing their cool on poor employees, and I have also been that same employee getting yelled at by customers when something goes awry, even if it's not the employee's fault. Trust me it's not fun being on the receiving end of that..
So kudos to you @thomasjmitchell for not being one of the people "flipping out" on the employee who was just trying to do their job.