Start by pulling video surveillance footage in the areas where the bricks “appear”. The bricks had to come from a company that makes bricks, no one makes bricks at home. Pallets sometimes have makers marks on them. Track down who paid for them, who transported them. This isn’t rocket science.
You don’t even need video. All you have to do is call the local masonry supply companies and ask them who ordered these pallets delivered. They have the order invoices which will be enough in court.