Dispatch advises that no one is supposed to be working late and that the owner will be there in 10 minutes. Since you have instructed the owner on how to respond in the past, you are not worried about him just walking up blindly.
You call for K-9 support but no one is available. You call for assistance from the next jurisdiction over and they advise the same thing. That means you are doing the building search. The third officer gets into position and you wait for the owner to arrive. If nothing else, this looks like a good opportunity to conduct some building search training.
When the owner arrives, you ask a few focused questions about who locked up, whether there are any disgruntled employees, and if he has had any work done to the place for which he may have given a key to a contractor. At first he doesn't come up with anything, but then remembers he had a contractor do some work several months ago. All the work was done on the weekends when the shop was closed and he let the contractor use a set of keys which were returned. You tell the owner to go back to his car and you ask for a clear channel in preparation to search the building.
Before you go in, you announce your presence and order whoever might be inside to come out. After several announcements and no response, you conduct your search. You don't find anyone and you clear emergency radio traffic and return the channel back to normal. You call in the owner and you have him identify any damage and or anything that might be missing.
Several locked glass cabinets have been smashed and a handful of low-end handguns are gone. He believes that several thousand dollars in coin collections and jewelry have been stolen as well. You ask about his surveillance system and after a quick check he advises it is up and running. Because of your agency policy, you don't process the scene but call out your crime scene techs.