What did Caesar say to Brutus when Brutus stabbed him?

According to Shakespeare, Caesar said "Et tu, Brute? Then fall, Caesar!" when his friend and adopted son Brutus stabbed him during the mass assassination that led to his death. "Et tu, Brute?" translates to "And you, Brutus?" meaning "even you, my son, have betrayed me."

Although the line has been made famous by Shakespeare, there is only one historical reference to Caesar making any remark as he was slain. In Suetonius's "De Vita Caesarum," Caesar allegedly said to Brutus, "And thou too, my son?" before covering his face with his toga and resigning himself to his fate. Because Suetonius was writing more than a century after the fact, it is possible this line is inaccurate or even apocryphal.