from the bond information it looks like they found no PC on the carrying charge, just on the DTP, weed, and trespass. He is lucky he didn't get charged with possession of a firearm with a CDS, that's a felony and could have stuck.
Leave means leave immediately. I bet if the response was "I'm sorry sir, if I place my weapon in my vehicle may I still shop?" the answer would have been "No problem". If the response would have been "Yes sir, we're leaving now" and you get in your vehicle and leave the premises there would have been no issues. However, if you play stupid games you win stupid prizes.
He should get this charge!