Maybe I'm naive but you said he was taking out of its case, if it was in a case, why was it loaded? Why was he transporting a loaded weapon? I'm guessing it wasn't his carry gun, since it was in a case. Maybe I'm wrong but either way, he should have removed the round in the chamber. The whole "I forgot it was loaded" nonsense has never worked with me. First rule of firearms: "treat every firearm as if it is loaded!" Therefore, there is never a reason to "forget it was loaded."
I agree with the OP, its frustrating when owners of firearms get careless and stop respecting their firearms. It makes us all look bad, especially now.