First things first, if the loss appears to be a result of a violation of the law, like theft, you should notify the police and file a report. You need to also notify the insurance company as soon as practical (prompt notice) and report the damage or loss. Be prepared to provide when, where, and how the loss occurred.
Next, you need to take immediate steps to protect property from further loss or damage. If you have to spend money on materials to protect the property, its important to keep track of expenses. If possible, take out your iPhone or Android and take some photos or video of the damage. Again, if possible, protecting the property from further damage should be priority.
You must furnish the insurance company (insurance adjuster) with inventories of damaged goods/property and undamaged goods/property. Be prepared to setup up a time with the adjuster, so that they can come out and do an inspection. This is where an inventory, pictures, and video of property prior to the loss can come in handy, so if you're reading this and have not had a loss, consider getting a camera out and opening up a spread sheet and conducting an inventory. You won't regret it should a loss ever occur.
Insured must file a proof of loss within sixty days of loss. This is a sworn state surrounding the facts of the loss. It might include information as to the time, place, cause of loss, value of property, and any other pertinent information. Usually the insurance company will furnish the form for the insured to complete and sign. The insurance adjuster can assist with the proof of loss form, if needed.
If you have any questions about Commercial Property Coverage, please feel free to contact me. It's always important to review your policy to ensure you understand what perils are covered and excluded. The last thing you want is to go through all of the above and find out Theft is excluded from the policy. Again, If you have questions, or need help, please let me know.