The engine is possibly locked up. The oil pressure dropped to zero before it stopped running.
The engine would need to be diagnosed to find the reason for it to seize up. The oil pressure dropping to zero is an indication that the oil pump may have failed, and starved the engine bearings of oil. If you ran the engine for more than a minute or two after losing oil pressure, then you may have spun the main and rod bearings. The engine would need to be completely overhauled or replaced, if this is the case.
I suggest having a certified mobile mechanic, such as one from YourMechanic, come to your home or place of business to determine the source and cause of the oil pressure issue, and provide a detailed inspection report that includes the scope and cost of any necessary repairs.
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