Which aria did baritone Leonard Warren sing on stage right before collapsing and dying?

Leonard Warren, leading baritone of the Metropolitan Opera, died last night on the stage where he had sung for more than twenty years.

The forty-nine-year-old singer collapsed as he was ending the second act of Verdi's "La Forza del Destino." He fell forward as he was making his exit at 10:05 p.m., and twenty-five minutes later the house physician pronounced him dead, victim of a stroke.
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At the time he collapsed, Mr. Warren had just finished the aria "O fatal pages of my destiny." He was singing the role of Don Carlo in the opera, set in Italy and Spain, and was dressed in the colorful uniform of a Spanish grenadier. The opera has a tragic ending in which Don Carlo is killed by an erstwhile friend.