I need an Expert - Dustin Hoffman Accident Question

Does anyone know what movie Dustin Hoffman was shooting when he accidentally shot himself with a real bullet while filming a scene?

This was a question from the game Scene It, but it does not say what movie he was filming, or how it happened. There is nothing on any of his biographies or on Google regarding this. It would seem like it would be more common knowledge.

I am hoping someone out there can help.

Thanks.