Baruch dayan ha'emet
Rabbi Marvin Hier, Dean and Founder of the Center, said,
"I think he'll be remembered as the conscience of the Holocaust. In a way he became the permanent representative of the victims of the Holocaust, determined to bring the perpetrators of the greatest crime to justice,". (Quotation from Ha'aretz.)
Many have written about his life much better than I can. Some links include:
Simon Wiesenthal Center Obituary
Biography of Wiesenthal's life (by the SWC)
Jerusalem Post Obituary
Comments by general people on Wiesenthal's life and death
[By the way, if you are unfamiliar with the phrase "baruch dayan ha'emet" it means "blessed is the true Judge" and is a phrase which many Jews say when they hear of a death.]
May his family find comfort in this difficult time.
May his soul rest with the Divine Holy One.