Car shuts off key stuck in ignition

First of all the engine didn't actually shuts off. When the warning lights started coming on my daughter stopped the car and turned it off. When she went to restart the car it was completely dead and the key was stuck in the ignition. When we took the battery cable off and then reconnected the terminals were very clean but, it solved the problem. We were able to remove the key and start the car and it seems fine. There are no lights on at all. We took it to see if maybe a code was stored but, there were no codes. Obviously something is wrong or this would not have happened. It almost seems as though it has to do with the anti theft feature shutting down the car but, we aren't sure? We have had the battery tested and it tested to be good. It seems we are definitely reseting the system when disconnecting the battery but, why is it happening to begin with?