Where can I learn more about Roque Gonz�lez de Santa Cruz?

I watched the movie The Mission, which I have found is only loosely based on his life. As I learned, he was actually killed by a Guarani witch doctor along with 2 fellow missionaries. Are there any good books or websites other than Wikipedia where I can learn more about his life and how the events really unfolded? I find myself drawn to learn more. His faith is incredibly fascinating to me.