I have that T Shirt too.
Many years ago I worked for the distribution side of a Major National Retailer. My main responsibility was running the warehouse management system that made sure that hundreds of people were able to pack and store the thousands of shipments that went through the great big building every day, each one of them on such tight timetables that so much as an hour of downtime on the management servers could cost the company millions in missed shipments, even if it happened on the weekend or in the middle of the night. My team took it pretty seriously and worked on designing a fairly bullet-proof system with multiple redundant hardware for everything, and it worked pretty well.
One morning I found an issue with the system which was causing some irregularities to show up in the daily reports. I have officially forgotten everything about it by now, but somewhere at the core of it were a number of scheduled jobs which exported data from the main database, pushed it from machine to machine, and made sure that every part of the system knew what every other part knew. If it didn't run then there would be slight inconsistencies on the first day, slightly more on the next, and if it hadn't run by the weekend then the application would completely fall over and someone who knew how it all worked would have to be called in to fix it. And it would have to be fixed _right now_ because of the costs associated with any down time.
I identified the problem and jumped right in to get it fixed. The first thing I did was set a "do not run" flag to make sure that nothing happened to make things worse before I was finished, and then made some notes which I would later enter into the incident ticket. Shortly after that my new manager dropped by and asked if he could see me right away.
"Um, okay. I'm kind of in the middle of something, can I drop by your office in about five minutes once I have this cleaned up?"
"No. I need to see you right now."
"Well... All right. I really have to get back to this once we're done."
As expected, the conversation was short and final. I asked what I could do to ensure a clean handover to whoever was getting stuck with my job after me, but told that I was being terminated immediately, would not be replaced and there would be no need for anything more and could I please just get out now and stop wasting time. Shortly after that I was escorted back to me desk accompanied by a security detail who were to make sure that I collected my things without touching my workstation in any way. The rest of my team had been conveniently pulled into a meeting so that they wouldn't be able to see what was happening and I ushered out the door without even being able to say goodbye.
To this day I have no idea just how much damage $FORMER_EMPLOYER did to themselves by handling everything this way, but that's really their problem, not mine.