oil pump failed

Sounds to me that the input hex in the pump is stripped, or the pressure relief valve is stuck open. If he had oil pressure to begin with, and can get 10 PSI out of it at 2000 RPM, the shaft didn't break, and the oil gallery plug must have been in there. I guess it could fail, or some other oiling oddball failure (not bearing or pump related), but, that would be pretty rare.