It's all from one of the employees, but here is what I got.
Guy, drunk off his McCaffery, comes into Jimmy Johns with a toaster and a loaf of bread. He's bragging about stealing both of them from a house party he was at. He wants them to give him the makings of a sandwich, but he doesn't need their bread, he stole his own. They wont give him the fixings, but they will sell him a sandwich and let him tear it apart if he wanted. He demanded to speak to a manager about the not-selling-him-handfulls-of-meat shenanigans, and the employee lied and said he was the manager. The drunk guy acquiesced and bought a sandwich.
He then plugged in the toaster in the little hallway of seats there, stuffed the toaster full of bread, and started it. When the over-stuffed toaster couldn't stop toasting because it was overstuffed, it started to smoke a little. He got scared, stood up, and walked out, leaving a smoking toaster in the back. He said that the toaster lit on fire, but there was no real damage.
Again, this is just what I heard from a guy who was working there at the time.